Quantum dot light enhancement substrate and lighting device including same

ABSTRACT

A component including a substrate, at least one layer including a color conversion material including quantum dots disposed over the substrate, and a layer including a conductive material (e.g., indium-tin-oxide) disposed over the at least one layer. (Embodiments of such component are also referred to herein as a QD light-enhancement substrate (QD-LES).) In certain preferred embodiments, the substrate is transparent to light, for example, visible light, ultraviolet light, and/or infrared radiation. In certain embodiments, the substrate is flexible. In certain embodiments, the substrate includes an outcoupling element (e.g., a microlens array). A film including a color conversion material including quantum dots and a conductive material is also provided. In certain embodiments, a component includes a film described herein. Lighting devices are also provided. In certain embodiments, a lighting device includes a film described herein. In certain embodiments, a lighting device includes a component described herein.

This application is a continuation of U.S. patent application Ser. No.15/055,827, filed 29 Feb. 2016, which is a continuation of U.S. patentapplication Ser. No. 14/311,542, filed 23 Jun. 2014, which is acontinuation of U.S. patent application Ser. No. 13/849,700, filed 25Mar. 2013 (now U.S. Pat. No. 8,759,850), which is a continuation of U.S.patent application Ser. No. 12/657,427, filed 20 Jan. 2010 (now U.S.Pat. No. 8,405,063), which is a continuation application of commonlyowned International Application No. PCT/US2008/008924, filed 23 Jul.2008, which was published in the English language as PCT Publication No.WO 2009/014707 on 29 Jan. 2009. PCT Application No. PCT/US2008/008924claims priority to U.S. Application No. 60/951,427, filed 23 Jul. 2007and U.S. Application No. 61/074,028, filed 19 Jun. 2008. Each of theforegoing applications is hereby incorporated herein by reference in itsentirety.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the technical fields of films includingquantum dots (QDs); components including quantum dots, which are usefulfor lighting applications; and devices including the foregoing.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, there isprovided a component comprising a substrate comprising a material thatis transparent to light within a predetermined range of wavelengths, acolor conversion material comprising quantum dots disposed over apredetermined region of a surface of the substrate, and a conductivematerial disposed over at least a portion of the color conversionmaterial, the conductive material being transparent to light within asecond predetermined range of wavelengths.

In certain embodiments, a component can include a substrate comprising amaterial that is transparent to light within a predetermined range ofwavelengths, a layer comprising a predetermined arrangement of featuresdisposed over a predetermined region of a surface of the substrate,wherein at least a portion of the features comprise a color conversionmaterial comprising quantum dots, and a conductive material disposedover at least a portion of the layer, the conductive material beingtransparent to light within a second predetermined range of wavelengths.In certain embodiments, features including color conversion material aredisposed in a dithered arrangement.

In certain embodiments, a component can include a substrate comprising amaterial that is transparent to light within a predetermined range ofwavelengths, a layered arrangement including two or more layers disposedover a predetermined region of a surface of the substrate, wherein eachof the layers comprises a color conversion material comprising quantumdots capable of emitting light having a predetermined wavelength that isdistinct from that emitted by quantum dots included in one or more ofthe other layers, and conductive material disposed over at least aportion of the layered arrangement, the conductive material beingtransparent to light within a second predetermined range of wavelengths.

In certain embodiments, one or more outcoupling features disposed on asurface of the substrate opposite the color conversion material.

In accordance with other embodiments of the present invention, there areprovided lighting devices including components described herein.

In accordance with another embodiment of the present invention, there isprovided a film comprising a layer comprising a color conversionmaterial comprising quantum dots and conductive material disposed overat least a portion of the layer.

In certain embodiments, a film comprises a conductive material and aplurality of features comprising a color conversion material disposedover at least a portion of the conductive material, wherein the colorconversion material comprises quantum dots and wherein the colorconversion material included in each of the features includes quantumdots capable of emitting light having a predetermined wavelength suchthat the film is capable of emitting light of a preselected color whenoptically coupled to a source of light emission. In certain embodiments,a preselected color of white is desirable.

In certain embodiments, a film comprises a layered arrangement of two ormore films comprising color conversion material, wherein colorconversion material includes quantum dots and wherein the colorconversion material included in each film is selected to include quantumdots capable of emitting light having a predetermined wavelength suchthat the layered arrangement is capable of emitting light of apreselected color when optically coupled to a source of light emission.In certain embodiments, films are arranged in order of decreasing orincreasing wavelength.

In accordance with other embodiments of the present invention, there areprovided components including films described herein.

In accordance with other embodiments of the present invention, there areprovided lighting devices including films described herein.

In accordance with another embodiments of the of the present invention,there is provided a lighting device including a component comprising asubstrate comprising a material that is transparent to light within apredetermined range of wavelengths, a color conversion materialcomprising quantum dots disposed over a predetermined region of asurface of the substrate, and a conductive material disposed over atleast a portion of the color conversion material, the conductivematerial being transparent to light within a second predetermined rangeof wavelengths, the conductive material forming a first electrode of thedevice; an emissive layer disposed over at least a portion of theconductive material, wherein the emissive layer comprises a materialcapable of emitting light; and a second electrode disposed over theemissive layer.

In various embodiments described herein, reference to light within apredetermined range of wavelengths includes light with a predeterminedwavelength.

Quantum dots comprising semiconductor nanocrystals are preferred for usein the present inventions.

The foregoing, and other aspects and embodiments described herein andcontemplated by this disclosure all constitute embodiments of thepresent invention.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention as claimed. Other embodimentswill be apparent to those skilled in the art from consideration of thespecification and practice of the invention disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIGS. 1 (a) and (b) schematically depict examples of embodiments of acomponent in accordance with the present invention.

FIG. 2 illustrates simulated spectra of an example of an embodiment of alight-emitting device that includes a blue Ph-OLED (fIr6) and threefilms including color conversion materials, each of which includesquantum dots capable of emitting light having a predeterminedwavelength.

FIG. 3 schematically depicts examples of embodiments of light emittingdevices in accordance with the present invention wherein the deviceincludes quantum dots in multi-layer-films ((a) and (c)) and inspatially dithered configurations ((b) and (d)).

The attached figures are simplified representations presented forpurposes of illustration only; the actual structures may differ innumerous respects, particularly including the relative scale of thearticles depicted and aspects thereof.

For a better understanding to the present invention, together with otheradvantages and capabilities thereof, reference is made to the followingdisclosure and appended claims in connection with the above-describeddrawings.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with one embodiment of the invention, there is provided afilm comprising a layer comprising a color conversion material CCMcomprising quantum dots and conductive material disposed over at least aportion of the layer.

In certain embodiments, the quantum dots comprise semiconductornanocrystals.

In certain embodiments, a film comprises a conductive material and aplurality of features comprising a color conversion material CCMdisposed over at least a portion of the conductive material, wherein thecolor conversion material CCM comprises quantum dots and wherein thecolor conversion material CCM included in each of the features isselected to include quantum dots capable of emitting light having apredetermined wavelength such that the film is capable of emitting lightof a preselected color when optically coupled to a source of lightemission.

In certain embodiments, the preselected color is white.

In certain embodiments, film comprises a layered arrangement of two ormore layers comprising color conversion material CCM, wherein colorconversion material CCM includes quantum dots and wherein the colorconversion material CCM included in each layer is selected to includequantum dots capable of emitting light having a predetermined wavelengthsuch that the film is capable of emitting light of a preselected colorwhen optically coupled to source of light emission. In certainembodiments, layers are arranged in order of decreasing or increasingwavelength.

In accordance with another embodiment of the present invention, there isprovided a component comprising a substrate SUB comprising a materialthat is transparent to light within a predetermined range ofwavelengths, a color conversion material CCM comprising quantum dotsdisposed over a predetermined region of a surface of the substrate SUB,and a conductive material disposed over at least a portion of the colorconversion material CCM, the conductive material being transparent tolight within a second predetermined range of wavelengths.

In certain embodiments, the quantum dots comprise semiconductornanocrystals.

In certain embodiments, the component includes two or more layerscomprising color conversion material CCM, wherein each layer comprises acolor conversion material CCM comprising quantum dots that are capableof emitting light having a predetermined wavelength that is distinctfrom light that can be emitted by quantum dots included in at least oneof the other layers.

In certain embodiments, a component comprises a substrate SUB comprisinga material that is transparent to light within a predetermined range ofwavelengths, a layer comprising a predetermined arrangement of featuresdisposed over a predetermined region of a surface of the substrate SUB,wherein at least a portion of the features comprise a color conversionmaterial CCM comprising quantum dots, and a conductive material disposedover at least a portion of the layer, the conductive material beingtransparent to light within a second predetermined range of wavelengths.

In certain preferred embodiments, the predetermined arrangementcomprises a dithered arrangement.

In certain embodiments, the predetermined arrangement includes featurescomprising color conversion material CCM and features comprisingmaterial with a refractive index that is not the same as that of thecolor conversion material CCM.

In certain embodiments, the predetermined arrangement includes featurescomprising color conversion material CCM and features comprisingmaterial with outcoupling capability.

In certain embodiments, the predetermined arrangement includes featurescomprising color conversion material CCM and features comprisingmaterial with outcoupling and non-scattering capability.

In certain embodiments, features comprising color conversion materialCCM are arranged in a dithered arrangement and wherein color conversionmaterial CCM included in each of the features is selected to includequantum dots capable of emitting light having a predetermined wavelengthsuch that the component is capable of emitting white light whenintegrated into a light source.

In certain embodiments, at least a portion of the features includingcolor conversion material CCM are optically isolated from other featuresincluding color conversion material CCM.

In certain embodiments, at least a portion of the features includingcolor conversion material CCM are optically isolated from other featuresincluding color conversion material CCM by air. For example, thefeatures may be spaced apart from each other. In certain embodiments,the spacing can be on a scale of millimeters to nanometers.

In certain embodiments, at least a portion of the features includingcolor conversion material CCM are optically isolated from other featuresincluding color conversion material CCM by a lower or higher refractiveindex material.

In certain embodiments, reflective material is included in spacesbetween at least a portion of the features including color conversionmaterial CCM.

In certain embodiments, the predetermined arrangement comprises featuresincluding color conversion material CCM, features comprising reflectivematerial, and features comprising scatterers.

In certain embodiments, a component comprises a substrate SUB comprisinga material that is transparent to light within a predetermined range ofwavelengths, a layered arrangement including two or more layers disposedover a predetermined region of a surface of the substrate SUB, whereineach of the layers comprises a color conversion material CCM comprisingquantum dots capable of emitting light having a predetermined wavelengththat is distinct from that emitted by quantum dots included in one ormore of the other layers, and conductive material disposed over at leasta portion of the layered arrangement, the conductive material beingtransparent to light within a second predetermined range of wavelengths,and one or more outcoupling features disposed on a surface of thesubstrate SUB opposite the color conversion material CCM.

In certain embodiments, a substrate SUB comprises a waveguide.

In certain embodiments, a substrate SUB is flexible.

In certain embodiments, a substrate SUB is rigid.

In certain embodiments, a component further includes a thin filminterference filter between the substrate SUB and color conversionmaterial CCM. Such filter can be useful to recycle unconverted lightback into the color conversion material CCM and to remove undesiredlight from light emitted from the component or device including same.

In certain embodiments, a component further includes one or moreoutcoupling features disposed on a surface of the substrate SUB oppositethe color conversion material CCM.

In certain embodiments, an outcoupling feature comprises a microlens.

In certain embodiments, an outcoupling feature comprises a micro-reliefstructure.

In certain embodiments, the component further includes an array ofoutcoupling features on a surface of the substrate SUB opposite thecolor conversion material CCM.

In certain embodiments, at least a portion of the outcoupling featuresare configured to have predetermined outcoupling angles.

In certain embodiments, at least a portion of the outcoupling featuresinclude a substantially hemispherical surface.

In certain embodiments, at least a portion of the outcoupling featuresinclude a curved surface.

In certain embodiments, at least a portion of the features are printed.

In certain embodiments, features can be printed by screen-printing,contract printing, or inkjet printing.

In certain embodiments of films, components, and devices describedherein, color conversion material CCM further comprises a host materialin which the quantum dots are dispersed. A non-limiting list of examplesof host materials are described below.

In certain embodiments, color conversion material CCM further comprisesa binder in which the quantum dots are dispersed.

In certain embodiments, color conversion material CCM has an index ofrefraction greater than or equal to the index of refraction of theconductive material.

In certain embodiments, the host material is transparent to light in thepredetermined range of wavelengths and light in the second predeterminedrange of wavelengths. For example, in certain embodiments, the hostmaterial is preferably at least 70%, more preferably at least 80%, andmost preferably at least 90%, transparent to light to be color convertedby the quantum dots. In certain embodiments, the host material ispreferably at least 70%, more preferably at least 80%, and mostpreferably at least 90%, transparent and light emitted by the quantumdots.

A host material can be an organic material or an inorganic material. Asmentioned above, non-limiting examples of host materials are providedherein.

In certain embodiments, a host material has an index of refractiongreater than or equal to the index of refraction of the conductivematerial.

In embodiments described herein including more than one color conversionmaterials CCMs, one or more of such materials can further include a hostmaterial. When more than one color conversion material CCM including ahost material is used, the host material in each can be the same hostmaterial. In certain embodiments, different host material can beincluded in one or more of the different color conversion materialsCCMs.

In certain embodiments, color conversion materials CCMs can furtherincludes scatterers.

In certain embodiments, light emitted from the surface of the componentis substantially uniform across a predetermined region of the substratesurface. In certain embodiments, white light is emitted.

In certain embodiments, a reflective material is included on the edgesof the substrate SUB.

In certain embodiments, a reflective material is included around atleast a portion of the edges of the substrate SUB.

Examples of reflective materials include silver and alumina Otherreflective materials can be used.

In certain embodiments including one or more layers comprising colorconversion material CCM, each layer is capable of emitting light at awavelength that is distinct from that of any of the other layers.

In certain embodiments including one or more layers including differentcolor conversion materials CCMs in a layered arrangement, the layers arearranged in order of decreasing wavelength from the conductive material,with the film capable of emitting light at the highest wavelength beingclosest to the conductive material and the film capable of emittinglight at the lowest wavelength being farthest from the conductivematerial.

In certain embodiments including a predetermined arrangement of featuresincluding color conversion materials CCMs, the light-emittingcharacteristics of the quantum dots included in color conversionmaterials CCMs included in the features can be selected based on thepreselected light output desired.

In certain embodiments, for example, a first portion of the featuresincludes quantum dots capable of emitting red light, a second portion ofthe features includes quantum dots capable of emitting orange light, athird portion of the features includes quantum dots capable of emittingyellow light, a fourth portion of the features includes quantum dotscapable of emitting green light, and a fifth portion of the featuresincludes quantum dots capable of emitting blue light

In another example, a first portion of the features includes quantumdots capable of emitting red light, a second portion of the featuresincludes quantum dots capable of emitting orange light, a third portionof the features includes quantum dots capable of emitting yellow light,a fourth portion of the features includes quantum dots capable ofemitting green light, and a fifth portion of the features includesoptically transparent scatterers or non-scattering material.

In another example, a first portion of the features includes quantumdots capable of emitting blue light, a second portion of the featuresincludes quantum dots capable of emitting green light, a third portionof the features includes quantum dots capable of emitting yellow light,and a fourth portion of the features includes quantum dots capable ofemitting red light.

In another example, a first portion of the features includes opticallytransparent scatterers or non-scattering material, a second portion ofthe features includes quantum dots capable of emitting green light, athird portion of the features includes quantum dots capable of emittingyellow light, and a fourth portion of the features includes quantum dotscapable of emitting red light.

In a further example, a first portion of the features includes quantumdots capable of emitting red light, a second portion of the featuresincludes quantum dots capable of emitting green light, and a thirdportion of the features includes quantum dots capable of emitting bluelight.

In still another example, a first portion of the features includesoptically transparent scatterers or non-scattering material, a secondportion of the features includes quantum dots capable of emitting redlight, and a third portion of the features includes quantum dots capableof emitting green light.

In yet another example, a first portion of the features includes quantumdots capable of emitting blue light, and a second portion of thefeatures includes quantum dots capable of emitting yellow light.

In a still further example, a first portion of the features includesoptically transparent scatterers or non-scattering material, and asecond portion of the features include quantum dots capable of emittingyellow light.

Other color conversion materials CCMs in other arrangements can also beused based on the light output desired and the color of the excitationlight for the quantum dots. For example, in the foregoing examples,arrangements including blue quantum dots can be used with an ultravioletlight source to provide a blue component of light in light emitted froma film, component, or device including such arrangement of features. Inthe foregoing examples, arrangements including scatterers and/ornonscattering materials and not blue quantum dots can be used with ablue light source, the blue source light providing the blue component oflight emitted from a film, component, or device including sucharrangement of features.

In certain embodiments including a layered arrangement of filmsincluding color conversion materials CCMs, the composition of, andnumber of, films can be selected based on the preselected light outputdesired and the excitation light source.

In certain embodiments, for example, a layered arrangement includes afirst film including quantum dots capable of emitting red light, asecond film including quantum dots capable of emitting orange light, athird film including quantum dots capable of emitting yellow light, afourth film including quantum dots capable of emitting green light, anda fifth film including quantum dots capable of emitting blue light.

In another example, a layered arrangement includes a first filmincluding quantum dots capable of emitting red light, a second filmincluding quantum dots capable of emitting orange light, a third filmincluding quantum dots capable of emitting yellow light, a fourth filmincluding quantum dots capable of emitting green light, and a fifth filmincluding scatterers or non-scattering material to outcouple light.

In another example, a layered arrangement includes a first filmincluding quantum dots capable of emitting blue light, a second filmincluding quantum dots capable of emitting green light, a third filmincluding quantum dots capable of emitting yellow light, and a fourthfilm including quantum dots capable of emitting red light.

In still another example, a layered arrangement includes a first filmincluding optically transparent scatterers or non-scattering material, asecond film including quantum dots capable of emitting green light, athird film including quantum dots capable of emitting yellow light, anda fourth film including quantum dots capable of emitting red light.

In a further example, a layered arrangement includes a first filmincluding quantum dots capable of emitting red light, a second filmincluding quantum dots capable of emitting green light, and a third filmincluding quantum dots capable of emitting blue light.

In a still further example, a layered arrangement includes a first filmincluding quantum dots capable of emitting red light, a second filmincluding quantum dots capable of emitting green light, and a third filmincluding scatterers or non-scattering material to outcouple light.

In yet another example, a layered arrangement includes a first filmincluding quantum dots capable of emitting blue light, a second filmincluding quantum dots capable of emitting yellow light.

In yet another example, a layered arrangement includes a first filmincluding quantum dots capable of emitting yellow light, a second filmincluding scatterers or non-scattering material to outcouple light.

Other color conversion materials CCMs in other layered arrangements canalso be used based on the light output desired and the color of theexcitation light for the quantum dots. For example, in the foregoingexamples, arrangements including blue quantum dots can be used with anultraviolet light source to provide a blue component of light in lightemitted from a film, component, or device including such arrangement offeatures. In the foregoing examples, arrangements including scatterersand/or nonscattering materials and not blue quantum dots can be usedwith a blue light source, the blue source light providing a bluecomponent of light in light emitted from a film, component, or deviceincluding such arrangement of features.

In accordance with other embodiments of the present invention, there areprovided components including one or more films described herein.

In accordance with other embodiments of the present invention, there areprovided lighting devices including one or more of the films and/orcomponents described herein.

In certain embodiments, in a lighting device including a componentdescribed herein, the conductive material can act as an electrode of thedevice.

Solid state lighting devices, including thin film light emitting devicessuch as OLEDs, quantum dot light emitting devices, thin filmelectroluminescent devices, are known in the art. The films andcomponents described herein are useful for improving these solid statelighting devices.

In certain embodiments, a lighting device includes a componentcomprising a substrate SUB comprising a material that is transparent tolight within a predetermined range of wavelengths, a color conversionmaterial CCM comprising quantum dots disposed over a predeterminedregion of a surface of the substrate SUB, and a conductive materialdisposed over at least a portion of the color conversion material CCM,the conductive material being transparent to light within a secondpredetermined range of wavelengths, the conductive material forming afirst electrode ELT1 of the device; an emissive layer EML disposed overat least a portion of the conductive material, wherein the emissivelayer comprises a material capable of emitting light; and a secondelectrode ELT2 disposed over the emissive layer.

In certain embodiments, a lighting device includes a componentcomprising a substrate SUB comprising a material that is transparent tolight within a predetermined range of wavelengths, a layer comprising apredetermined arrangement of features disposed over a predeterminedregion of a surface of the substrate SUB, wherein at least a portion ofthe features comprise a color conversion material CCM comprising quantumdots, and a conductive material disposed over at least a portion of thelayer, the conductive material being transparent to light within asecond predetermined range of wavelengths, the conductive materialforming a first electrode ELT1 of the device; an emissive layer EMLdisposed over at least a portion of the conductive material, wherein theemissive layer EML comprises a material capable of emitting light; and asecond electrode ELT2 disposed over the emissive layer.

In certain embodiments, a lighting device includes a componentcomprising a substrate SUB comprising a material that is transparent tolight within a predetermined range of wavelengths, a layered arrangementincluding two or more layers disposed over a predetermined region of asurface of the substrate SUB, wherein each of the layers comprises acolor conversion material CCM comprising quantum dots capable ofemitting light having a predetermined wavelength that is distinct fromthat emitted by quantum dots included each of the other layers, andelectrode material disposed over at least a portion of the layeredarrangement, the conductive material being transparent to light within asecond predetermined range of wavelengths, the conductive materialforming a first electrode ELT1 of the device; an emissive layer disposedover at least a portion of the conductive material, wherein the emissivelayer comprises a material capable of emitting light; and a secondelectrode ELT2 disposed over the emissive layer.

In such embodiments, a device can further include one or more chargetransport layers between the electrodes.

In such embodiments, a device can further include one or more chargeinjection layers between the electrodes.

In certain of such embodiments, an emissive layer can comprise quantumdots.

In certain of such embodiments, an emissive layer can comprise anorganic electroluminescent material.

In certain of such embodiments, an emissive layer can comprise anelectroluminescent phosphor.

In certain embodiments, a substrate SUB included in component includedin a lighting device further includes one or more outcoupling featureson a surface of the substrate SUB opposite the color conversion materialCCM.

In certain embodiments, the emissive layer included in a device iscapable of emitting blue light.

In certain embodiments, the emissive layer included in a device iscapable of emitting ultraviolet light.

In certain embodiments, the emissive layer included in a device iscapable of emitting light with a predetermined wavelength.

In certain embodiments, composition and arrangement of color conversionmaterials CCMs included in a component included in a lighting device ispreselected for achieving the desired light output from the device.Non-limiting examples are described above.

In certain embodiments, a film, device, and component described hereincan further include a UV filter to remove UV light from light emittedfrom the device from which UV emission could occur.

In certain embodiments of films, devices, and/or components describedherein including a layered arrangement including two or more filmsincluding color conversion material CCM, the films are arranged in orderof decreasing wavelength. Preferably, the film capable of emitting lightat the highest wavelength being closest to the conductive material andthe film capable of emitting light at the lowest wavelength beingfarthest from the conductive material.

In certain embodiments of films, devices, and/or components describedherein, the color conversion material CCM can absorb at least 70% morepreferably, at least 80%, and most preferably, at least 90%, of light tobe color converted.

In certain embodiments, a color conversion material CCM includes quantumdots without a host material. In certain of such embodiments, colorconversion material CCM preferably has a thickness of less than about 10microns, and more preferably less than one micron.

In certain embodiments, a color conversion material CCM includes quantumdots distributed in a host material. In certain of such embodiments, forexample, including about 2-3 weight percent quantum dots based on theweight of the host material, color conversion material CCM preferablyhas a thickness of less than about 100 microns, and more preferably lessthan 70 microns. In certain embodiments, the thickness can be in a rangefrom about 40-70 or 50-60 microns.

Concentrations, thickness, and configurations, etc. will vary based onthe materials used, performance criteria, and other design choices.

In certain embodiments including a host material, the host materialpreferably has an index of refraction greater than or equal to that ofthe conductive material being used.

In certain embodiments of films, components, and devices describedherein including features including color conversion material CCM, afeature can be submicron (e.g., less than 1 micron). In certainembodiments, a feature can have a size in the range from about 100 nm toabout 1 micron. Other sized may also be desired based on the applicationand desired light effect.

In certain embodiments of films, components, and devices describedherein, the conductive material is disposed in a second predeterminedarrangement. For example, in certain embodiments a conductive materialcan be patterned or unpatterned. In patterned embodiments, a feature ofthe pattern can have a size less than or equal to about 10 cm, less thanor equal to about 1 cm, less than or equal to about 1 mm, less than orequal to about 100 microns. Other size features can also be used. Anunpatterned area of conductive material and a feature of patternedconductive material may be referred to for purposes of this discussionas a pixel. In certain embodiments, the size of the features comprisingcolor conversion material CCM can be submicron, which can besignificantly smaller than the size of the features of the conductivematerial. This can permit dithering of features of color conversionmaterial CCM within the area of a corresponding pixel of conductivematerial.

As discussed above, in certain embodiments, a component includes asubstrate SUB, at least one layer including a color conversion materialCCM comprising quantum dots disposed over the substrate SUB, and a layercomprising a conductive material (e.g., indium-tin-oxide) disposed overthe at least one layer. (Such component is also referred to herein as aQD light-enhancement substrate (QD-LES).) In certain preferredembodiments, the substrate SUB is transparent to light, for example,visible light, ultraviolet light, and/or infrared radiation. In certainembodiments, the substrate SUB is flexible. In certain embodiments, thesubstrate SUB includes an outcoupling element. In certain embodiments,the substrate SUB includes an optical member (e.g., a microlens arrayMLA). In certain embodiments, the substrate SUB has a microlens arrayMLA on the light-emitting surface thereof. In certain embodiments, theat least one layer comprising quantum dots is patterned. In certainembodiments, the at least one layer comprising quantum dots isunpatterned. In certain preferred embodiments, the at least one layercomprises a solution-processable quantum dots.

In accordance with another aspect of the present invention, there isprovided a light emitting device including a component described herein.In certain embodiments, the component includes at least one layerincluding quantum dots (QDs). In certain embodiments, the at least onelayer comprising quantum dots is patterned. In certain embodiments, theat least one layer comprising quantum dots is unpatterned. In certainpreferred embodiments, the at least one layer comprises asolution-processable quantum dots. In certain embodiments, the lightemitting device includes a substrate SUB comprising at least one layercomprising quantum dots disposed over the substrate SUB, and a layercomprising indium-tin-oxide (ITO) disposed over the at least one layer.In certain embodiments, the substrate SUB is flexible. In certainembodiments, the substrate SUB includes an outcoupling element. Incertain embodiments, the substrate SUB includes a microlens array MLA.In certain embodiments, the substrate SUB has a microlens array MLA onthe light-emitting surface thereof. In certain preferred embodiments,the substrate SUB is transparent to light, for example, visible light,ultraviolet light, and/or infrared radiation. In certain embodiments,the light emitting device comprises an organic light emitting device(OLED). In certain embodiments comprising an OLED, the OLED can achieveefficient and stable color rendering index (CRI), which can be desirablefor various solid state lighting applications. In certain embodiments,the at least one layer including quantum dots is capable of generatingtunable white emission from a light emitting device that emits bluelight (see FIG. 1(a) for an example of one embodiment), including, butnot limited to an OLED. FIG. 1(a) schematically depicts an example of anembodiment of a quantum dot light enhancement substrate (QD-LES)incorporating films comprising quantum dots capable of emitting lighthaving a wavelength distinct from that emitted by quantum dots in otherfilms In certain embodiments, the quantum dots are dispersed in a hostmaterial. Preferably the host material has a refractive index greaterthan or equal to that of the conductive material. The quantum dotcontaining films are disposed between a transparent conductive orelectrode material (e.g., an ITO film; ITO has a refractive index of1.8) and a base material comprising, for example, glass or othermaterial with desired transparency.

In certain embodiments, moisture and oxygen getters or desiccant can beincluded in a film, component, or device included herein.

In certain embodiments, a protective environmental coating may also beapplied to the emitting face of a film, component, or device to protectthe color conversion material CCM from the environment.

In the example of the embodiment depicted in FIG. 1(a), the layercomprising quantum dot (QD) integrated into ITO-glass substrates canalter the emission from, e.g., a blue emitting phosphorescent OLED(Ph-OLED) device, and outcouple light from the ITO film.

In certain embodiments, an outcoupling element OCE is further includedin or on the external surface of the substrate SUB. A preferred exampleof an outcoupling element OCE comprises a microlens array MLA. Anexample of an embodiment including a substrate SUB including a microlensarray MLA is illustrated in FIG. 1(b). In the example depicted in FIG.1(b), a quantum dot light enhancement substrate (QD-LES) includes filmscomprising quantum dots capable of emitting light having a wavelengthdistinct from that emitted by quantum dots in other films In certainembodiments, the quantum dots are dispersed in a host material.Preferably the host material has a refractive index greater than orequal to that of the conductive material. The quantum dot containingfilms are disposed between a transparent electrode (e.g., an ITO film)and a base material comprising, for example, glass or other materialwith desired transparency. A microlens array MLA is also included toimprove outcoupling of light.

(While the examples of embodiments shown in FIGS. 1 (a) and (b) depictbottom-emitting OLED structures on glass substrates SUB, in otherembodiments, in other embodiments, the substrate can be flexible and/orthe OLED structure can be top-emitting OLED.).

In the examples depicted in FIG. 1, three films including quantum dotsare included in the component. In certain embodiments, fewer films canbe included. In certain embodiments, more than three films can beincluded. The number of films is a design choice based on thepredetermined spectral output desired from the component.

In certain embodiments comprising an OLED, the substrate SUB includingquantum dots will simultaneously increase OLED light out-coupling whilepreferably providing >85 CRI white light, more preferably >90 CRI, andmost preferably >95, white light, that is readily tunable and inherentlystable for any diffuse lighting application.

In certain embodiments comprising an OLED, OLED external quantumefficiencies can be improved by potentially more than 100% whileproducing high CRI white light with enhanced stability performance overa wide range of intensities. In certain embodiments, as shown in FIG. 2,a CRI>95 white light with unprecedented color stability performance overa wide range of intensities may be achieved. FIG. 2 provides a simulatedspectra of a CRI=86 QD-LES (including three films including quantumdots) optically coupled to a blue Ph-OLED (fIr6). The simulation isbased in inclusion of a red-emitting film, a yellow-emitting film, and agreen-emitting film. A 5500K black body radiation curve is also plottedfor reference.

In certain embodiments, a film or layer comprising quantum dot isdirectly applied to a substrate SUB by solution processing techniques.Preferably, the refractive index of the film or layer comprising quantumdots is greater than the refractive index of the substrate SUB overwhich the film or layer is disposed and is greater than the refractiveindex of the layer of conductive material (e.g., indium-tin-oxide (ITO))which is disposed over the film or layer comprising quantum dots.Preferably, the inclusion of the film or layer comprising quantum dotsbetween the substrate SUB and the conductive layer (e.g., ITO) canprovide unprecedented increases in light extraction efficiencies whenincluded in an OLED along with stable, high (preferably >85, morepreferably >90, most preferably >95) CRI white light.

Since the publication of multilayered organic electroluminescent (EL)devices in 1987 (C. W. Tang, S. A. VanSlyke, Appl. Phys. Lett. 1987, 51,913), the development of OLED materials and device architectures hasdriven continuous advancements in EL device efficiencies. In fact, whenBaldo et. al. introduced the use of phosphorescent emitters (M. A.Baldo, S. Lamansky, P. E. Burrows, M. E. Thompson, and S. R. Forrest,Appl. Phys. Lett. 1999, 75, 4. T. Tsutsui et al, Jpn. J. Appl. Phys.,Part 2 1999, 38, L1502.)

Ph-OLED devices were shown to operate with nearly 100% internal quantumefficiencies. However, only a fraction of the total photons generated inthese devices are usefully extracted because of the total internalreflection (TIR) and wave-guiding effects of the high-index layerscomprising the device and anode. The loss mechanism is associated withthe absorption of the reflected and wave-guided photons by the metalelectrode, the organic layers themselves, and the indium tin oxide (ITO)electrode. Consequently, the measured external quantum efficiencies ofthese devices are typically only ˜20% of the internal efficiency (T.Tsutsui, E. Aminaka, C. P. Lin, D.-U. Kim, Philos. Trans. R. Soc. LondonA 1997, 355, 801, N. K. Patel, S. Cina, J. H. Burroughes, IEEE J. Sel.Top. Quantum Electron. 2002, 8, 346)

While many methods have been proposed and attempted to increase thelight out-coupling efficiency within an OLED device structure,considerable improvements are still needed to enable OLEDs to achievethe performance and cost needed to enter the solid state lighting (SSL)market.

While increases in extraction efficiency have been realized,considerable room for improvement remains.

In accordance with certain preferred embodiments of the invention, aplanar, composite material including quantum dots dispersed therein isincluded in a substrate SUB for a blue-emitting ph-OLED. In certainembodiments, the composite material including quantum dots has arefractive index that is at least 0.1 higher, preferably at least 0.2higher, more preferably at least 0.3 higher than the substrate SUB. Incertain embodiments further including a layer of ITO disposed over theone or more layers including quantum dots, the index of refraction ofthe composite including quantum dots is also at least 0.1 higher,preferably at least 0.2 higher, more preferably at least 0.3 higher thanthe ITO layer. The composite material including quantum dots dispersedtherein is capable of down-converting a precisely tailored portion ofthe blue light emitted by the ph-OLED to create white light, mostpreferably with a high CRI (e.g., at least 85, at least 90, at least95), while out-coupling light typically lost at an interface between ITOand the substrate SUB on which it is deposited. Optical modes within theOLED will preferentially propagate within one or more layers or filmsincluding quantum dots by tailoring the refractive index and thicknessof the composite. In certain preferred embodiments, appropriatescattering materials are further included within the composite. Suchscatterers can enhance light extraction from the device. Additionalinformation that may be useful for the present inventions is describedin U.S. Patent Application Nos. 60/946,090, entitled “Methods ForDepositing Nanomaterial, Methods for Fabricating A Device, Methods ForFabricating An Array Of Devices and Compositions, of Linton, et al.,filed 25 Jun. 2007; 60/949,306, entitled “Methods For DepositingNanomaterial, Methods for Fabricating A Device, Methods For FabricatingAn Array Of Devices and Compositions, of Linton, et al., filed 12 Jul.2007; 60/971,885, entitled “Optical Component, System Including anOptical Components, Devices, and Composition”, of Coe-Sullivan, et al.,filed 12 Sep. 2007; 60/973,644, entitled “Optical Component, SystemIncluding an Optical Components, Devices, and Composition”, ofCoe-Sullivan, et al., filed 19 Sep. 2007; and 61/016,227, entitled“Compositions, Optical Component, System Including an OpticalComponents, and Devices”, of Coe-Sullivan, et al., filed 221 Dec. 2007;each of the foregoing being hereby incorporated herein by reference inits entirety. This innovative solution will simultaneously increaselight-extraction efficiency and generate tunable, high CRI, white lightvia multiple narrow band QD emitters.

In certain embodiments, a layer comprising color conversion material CCMincluding quantum dots (e.g., a quantum dot-light enhancement film(QD-LEF)) can further include scatterers. In certain embodiments, thescatterers can be included in the color conversion material CCM. Incertain embodiments, the scatterers can be included in a separate layer.In certain embodiments, a film or layer including a color conversionmaterial CCM can be disposed in a predetermined arrangement includingfeatures wherein a portion of the features includes scatterers but donot include color conversion material CCM. In such embodiments, thefeatures including color conversion material CCM can optionally alsoinclude scatterers.

Examples of scatterers (also referred to as light scattering particles)that can be used in the embodiments and aspects of the inventionscontemplated by this disclosure, include, without limitation, metal ormetal oxide particles, air bubbles, and glass and polymeric beads (solidor hollow). Other scatterers can be readily identified by those ofordinary skill in the art. In certain embodiments, scatterers have aspherical shape. Preferred examples of scattering particles include, butare not limited to, TiO₂, SiO₂, BaTiO₃, BaSO₄, and ZnO. Particles ofother materials that are non-reactive with the host material and thatcan increase the absorption pathlength of the excitation light in thehost material can be used. Additionally, scatterers that aid in theout-coupling of the down-converted light may be used. These may or maynot be the same scatterers used for increasing the absorptionpathlength. In certain embodiments, the scatterers may have a high indexof refraction (e.g., TiO₂, BaSO₄, etc) or a low index of refraction (gasbubbles). Preferably the scatterers are not luminescent.

Selection of the size and size distribution of the scatterers is readilydeterminable by those of ordinary skill in the art. The size and sizedistribution is preferably based upon the refractive index mismatch ofthe scattering particle and the host material in which it the scattereris to be dispersed, and the preselected wavelength(s) to be scatteredaccording to Rayleigh scattering theory. The surface of the scatteringparticle may further be treated to improve dispersability and stabilityin the host material. In one embodiment, the scattering particlecomprises TiO₂ (R902+ from DuPont) of 0.2 μm (micron) particle size, ina concentration in a range from about 0.001 to about 20% by weight. Incertain preferred embodiments, the concentration range of the scatterersis between 0.1% and 10% by weight. In certain more preferredembodiments, a composition includes a scatterer (preferably comprisingTiO₂) at a concentration in a range from about 0.1% to about 5% byweight, and most preferably from about 0.3% to about 3% by weight.

In embodiments including a layer comprising quantum dots dispersed in acomposite or host material, preferred composite or host materialsinclude those which are optically transparent and have a refractiveindex of at least 1.6. In certain preferred embodiments, the compositeor host material has an index of refraction in the range from 1.6 to2.1. In certain other embodiments, the composite or host material has anindex of refraction of at least 1.8. Examples include inorganic matricessuch as silicon nitride.

Examples of a host material useful in various embodiments and aspect ofthe inventions described herein include polymers, monomers, resins,binders, glasses, metal oxides, and other nonpolymeric materials. Incertain embodiments, an additive capable of dissipating charge isfurther included in the host material. In certain embodiments, thecharge dissipating additive is included in an amount effective todissipate any trapped charge. In certain embodiments, the host materialis non-photoconductive and further includes an additive capable ofdissipating charge, wherein the additive is included in an amounteffective to dissipate any trapped charge. Preferred host materialsinclude polymeric and non-polymeric materials that are at leastpartially transparent, and preferably fully transparent, to preselectedwavelengths of visible and non-visible light. In certain embodiments,the preselected wavelengths can include wavelengths of light in thevisible (e.g., 400-700 nm), ultraviolet (e.g., 10-400 nm), and/orinfrared (e.g., 700 nm-12 μm) regions of the electromagnetic spectrum.Preferred host materials include cross-linked polymers and solvent-castpolymers. Examples of preferred host materials include, but are notlimited to, glass or a transparent resin. In particular, a resin such asa non-curable resin, heat-curable resin, or photocurable resin issuitably used from the viewpoint of processability. As specific examplesof such a resin, in the form of either an oligomer or a polymer, amelamine resin, a phenol resin, an alkyl resin, an epoxy resin, apolyurethane resin, a maleic resin, a polyamide resin, polymethylmethacrylate, polyacrylate, polycarbonate, polyvinyl alcohol,polyvinylpyrrolidone, hydroxyethylcellulose, carboxymethylcellulose,copolymers containing monomers forming these resins, and the like. Othersuitable host materials can be identified by persons of ordinary skillin the relevant art. Preferably a host material is not a metal.

In certain embodiments, a host material comprises a photocurable resin.A photocurable resin may be a preferred host material in certainembodiments in which the composition is to be patterned. As aphoto-curable resin, a photo-polymerizable resin such as an acrylic acidor methacrylic acid based resin containing a reactive vinyl group, aphoto-crosslinkable resin which generally contains a photo-sensitizer,such as polyvinyl cinnamate, benzophenone, or the like may be used. Aheat-curable resin may be used when the photo-sensitizer is not used.These resins may be used individually or in combination of two or more.

In certain embodiments, a color conversion material CCM includingquantum dots further comprises a host material in which the quantum dotsare dispersed. In certain embodiments, the composition includes fromabout 0.001 to about 15 weight percent quantum dots based on the weightof the host material. In certain embodiments, the composition includesfrom about 0.1 to about 5 weight percent quantum dots based on theweight of the host material. In certain embodiments, the compositionincludes from about 1 to about 3 weight percent quantum dots based onthe weight of the host material. In certain embodiments, the compositionincludes from about 2 to about 2.5 weight percent quantum dots based onthe weight of the host material. In certain embodiments, the scatterersare further included in the composition in amount in the range fromabout 0.001 to about 15 weight percent based on the weight of the hostmaterial. In certain embodiments, the scatterers are included in amountin the range from about 0.1 to 2 weight percent based on the weight ofthe host material. In certain embodiments, a host material comprises abinder. Examples of host materials are provided herein.

In certain embodiments, a host material comprises a solvent-cast resin.A polymer such as a polyurethane resin, a maleic resin, a polyamideresin, polymethyl methacrylate, polyacrylate, polycarbonate, polyvinylalcohol, polyvinylpyrrolidone, hydroxyethylcellulose,carboxymethylcellulose, copolymers containing monomers forming theseresins, and the like can be dissolved in solvents known to those skilledin the art. Upon evaporation of the solvent, the resin forms a solidhost material for the semiconductor nanoparticles. In certainembodiments, the color conversion material CCM including quantum dots(e.g., semiconductor nanocrystals) and a host material can be formedfrom an ink composition comprising quantum dots and a liquid vehicle,wherein the liquid vehicle comprises a composition including one or morefunctional groups that are capable of being cross-linked. The functionalunits can be cross-linked, for example, by UV treatment, thermaltreatment, or another cross-linking technique readily ascertainable by aperson of ordinary skill in a relevant art. In certain embodiments, thecomposition including one or more functional groups that are capable ofbeing cross-linked can be the liquid vehicle itself. In certainembodiments, it can be a co-solvent. In certain embodiments, it can be acomponent of a mixture with the liquid vehicle. In certain embodiments,the ink can further include scatterers.

In certain embodiments, quantum dots (e.g., semiconductor nanocrystals)are distributed within the host material as individual particles.Preferably the quantum dots are well-dispersed in the host material.

In certain embodiments, outcoupling members or structures may also beincluded. In certain embodiments, they can be distributed across asurface of the substrate opposite the color conversion material CCMand/or in features in a layer including features including colorconversion material CCM. In certain preferred embodiments, suchdistribution is uniform or substantially uniform. In certainembodiments, coupling members or structures may vary in shape, size,and/or frequency in order to achieve a more uniform light distribution.In certain embodiments, coupling members or structures may be positive,i.e., sitting above the surface of the substrate, or negative, i.e.,depressed into the surface of the substrate, or a combination of both.In certain embodiments, one or more features comprising a colorconversion material CCM can be applied to a surface of a positivecoupling member or structure and/or within a negative coupling member orstructure.

In certain embodiments, coupling members or structures can be formed bymolding, embossing, lamination, applying a curable formulation (formed,for example, by techniques including, but not limited to, spraying,lithography, printing (screen, inkjet, flexography, etc), etc.) Colorconversion materials CCMs including quantum dots and/or films or layersincluding such color conversion materials CCMs can be applied toflexible or rigid substrates. Examples of deposition methods includemicrocontact printing, inkjet printing, etc. The combined ability toprint colloidal suspensions including quantum dots over large areas andto tune their color over the entire visible spectrum makes them an ideallumophore for solid-state lighting applications that demand tailoredcolor in a thin, light-weight package. Intrinsic QD lifetimes under UVphoto-luminescent stress conditions of at least 10,000 hours (with nosignificant change in brightness), demonstrate the great potential forthese printable, inorganic chromophores. An InP/ZnSeS core/shell QD canshow similar lifetime performance under similar conditions as shown herefor the CdSe systems. The demonstrated photostability properties ofquantum dots along with the recent advancements in solid-state quantumyield enable of the above-proposed application of quantum dots. Incertain embodiments, a light-emitting device including a component inaccordance with the invention including a substrate including at leastone layer comprising quantum dots can achieve improved CRI(preferably >85, more preferably >90, most preferably >95) and >90%improvement in external quantum efficiency. In certain preferredembodiments, the device including at least one layer comprising quantumdots disposed over a substrate, and a light-emitting device includingsame is RoHS compliant.

In certain embodiments including a color conversion material CCMcomprising quantum dots dispersed in a composite or host material, thequantum dots will including one or more surface capping ligands attachedto a surface of the quantum dots that are chemically compatibility withthe composite or host material. The composite or host material caninclude an organic or inorganic material. In certain embodiments, adevice will include more than one composite or host material includingquantum dots, wherein each of the quantum dot/composite or hostmaterials combinations is capable of emitting light having a wavelengththat is distinct from that emitted by any of the other quantumdot/composite or host material combinations. Preferably a deviceincludes three different quantum dot/composite or host materialcombinations, each of which emits at a predetermined specific wavelengththat is distinct from that of the others included in the device; morepreferably 4 different quantum dot/composite or host materialcombinations, and most preferably, more than 4. The color of the quantumdot emission will include tuning the core emission while maintainingsize distribution and quantum efficiency and then growing a thick,graded, alloy shell onto the cores to maximize quantum efficiency andsolid state stability. Achieving quantum efficiencies of at least 80% insolution and preserving that efficiency in the solid state hostmaterials will be very important to the success of this development.

In certain embodiments, a component (e.g., a QD-LES) will be RoHScompliant. The RoHS limits are readily identified by one of ordinaryskill in the relevant art. In certain preferred embodiments, a componentis cadmium free.

High quantum efficiencies (>85%) of Cd-based quantum dots in solutionhave been achieved. By selecting QD materials that are chemicallycompatibility with a host material, QDs have been dispersed into varioussolid materials while maintaining quantum efficiencies of over 50% inthe solid state. To maintain high quantum efficiency of QDs, it ispreferred to attach capping ligands to quantum dots that are compatiblewith the chemical nature of the host material, be that an organic orinorganic material.

In certain embodiments, including a color conversion material CCMincluding quantum dots dispersed in a host material, the quantum dots,prior to being included in the host material, preferably have a quantumefficiency of at least 85%. In certain embodiments, a color conversionmaterial CCM comprising a host material including QD dispersed thereinhas a quantum efficiency over 50% in the solid state. In certainembodiments, at least a portion of the quantum dots include one or moreligands attached to a surface thereof that are chemically compatibilitywith a host material. To maintain high quantum efficiency of QDs, it ispreferred to attach capping ligands to quantum dots that are compatiblewith the chemical nature of the host material, be that an organic orinorganic material.

In certain embodiments, a color conversion layer includes an amount QDsper area effective to preferably achieve greater than or equal to about70%, more preferably greater than or equal to about 80%, and mostpreferably greater than or equal to about 90%, absorption.

In certain embodiments, quantum dots comprise Cd-free QD materials.

The transition from a liquid to a solid dispersion can affect QDefficiencies. It is believed that the speed of this transition isimportant to maintaining high quantum efficiency, as the ratecompetition “locks” the QDs into place before aggregation or otherchemical effects can occur. Chemically matching the QDs to the hostmaterial and controlling the speed of “cure” are believed to be affectquantum efficiency. In certain embodiments, QDs are dispersed in organichost materials such as polymethylmethacrylate (PMMA) and polysiloxanes.For other quantum dot materials and hosts that may be useful with thepresent invention, see also Lee, et al., “Full Color Emission From II-VISemiconductor Quantum-Dot Polymer Composites”. Adv. Mater. 2000, 12, No.15 August 2, pp. 1102-1105, the disclosure of which is herebyincorporated herein by reference.

For solid state light applications, film lifetime and index ofrefraction will be important to performance. In certain embodiments, QDswill be dispersed in an inorganic film (TiO₂, for example). Chemicallymatching the QDs to the inorganic host material and controlling thespeed of “cure” will enhance performance. In certain embodiments, thecomposite or host material can comprise an organic host material such aspolysiloxanes.

Prior to the present invention, approaches to increasing lightextraction efficiency in OLEDs have included:

-   -   (1) Modifying the substrate surface to reduce TIR loss at the        substrate/air interface—e.g. with polymer micro-lenses (S.        Moller and S. R. Forrest, J. Appl. Phys. 2002, 91, 3324), large        area hemispherical lenses (C. F. Madigan, M.-H. Lu, and J. C.        Sturm, Appl. Phys. Lett. 2000, 76, 1650), silica microspheres        (T. Yamasaki, K. Sumioka, and T. Tsutsui, Appl. Phys. Lett.        2000, 76, 1243), or mesa structured devices (G. Gu, D. Z.        Garbuzov, P. E. Burrows, S. Vankatsh, S. R. Forrest, and M. E.        Thompson, Opt. Lett. 1997, 22, 396).    -   (2) Modifying the substrate to reduce TIR loss at the        substrate/ITO interface—e.g. by inserting a low-refractive index        silica aerogel porous layer between the ITO and glass substrate        (T. Tsutsui, M. Tahiro, H. Yokogawa, K. Kawano, and M. Yokoyama,        Adv. Mater. 2001, 13, 1149 and H. Yokogawa, K. Kawano, M.        Yokoyama, T. Tsutsui, M. Yahiro, and Y. Shigesato, SID Int.        Symp. Digest Tech. Papers 2001, 32, 405) or by using a high        refractive index substrate (T. Nakamura, N. Tsutsumi, N. Juni,        and H. Fugii, J. Appl. Phys. 2005, 97, 054505).    -   (3) Utilizing 2-D photonic crystal (PC) patterns in one or        multiple layers within the device structure to reduce        waveguiding modes and enhance light out-coupling normal to the        substrate surface (Y.-J. Lee, S.-H. Kim, J. Huh, G.-H. Kim,        Y.-H. Lee, S.-H. Cho, Y.-C. Kim, Y. R. Do, Appl. Phys. Lett.        2003, 82, 3779; Y. R. Do, Y. C. Kim, Y.-W. Song, C.-O. Cho, H.        Jeon, Y.-J. Lee, S.-H. Kim, Y.-H. Lee, Adv. Mater. 2003, 15,        1214; Y. R. Do, Y.-C. Kim, Y.-W. Song, Y.-H. Lee, J Appl. Phys.        2004, 96, 7629; Y.-C. Kim, S.-H. Cho, Y.-W. Song, Y.-J. Lee,        Y.-H. Lee, Y. R. Do, Appl. Phys. Lett. 2006, 89, 173502; M.        Fujita, K. Ishihara, T. Ueno, T. Asano, S. Noda, H. Ohata, T.        Tsuji, H. Nakada, N. Shimoji, Jpn. J. Appl. Phys. 2005, 44,        3669; and K. Ishihara, M. Fujita, I. Matsubara, T. Asano, S.        Noda, H. Ohata, A. Hirasawa, H. Nakada, N. Shimoji, Appl. Phys.        Lett. 2007, 90, 111114.    -   (4) Fabricating micro-cavity structures within the OLED device        structure (R. H. Jordan, L. J. Rothberg, A. Dodabalapur,        and R. E. Slusher, Appl. Phys. Lett. 1996, 69, 1997; and H. J.        Peng, M. Wong, and H. S. Kwok, SID Int. Symp. Digest Tech.        Papers 2003, 34, 516).

Despite the fact that all of these approaches have been shown toincrease light extraction efficiency, they all have several drawbacks.The approaches in the first category are able to recover the waveguidedlight confined within the substrate but fail to harness the largercomponent localized in the high refractive index organic and ITO layers.The methods within the second category aim to out-couple the high-indexmode light, but the results to date have suffered from an inability toadequately match the refractive index of ITO and effectively reduce theTIR at the ITO/substrate interface (T. Nakamura, N. Tsutsumi, N. Juni,and H. Fugii, J. Appl. Phys. 2005, 97, 054505). Categories three andfour typically suffer from strong angular-dependent emission and the PCdevices in category three can also be plagued by changes in electricalcharacteristics, complex processing requirements, and high cost.

To date the largest observed enhancements in extraction efficiency havebeen in a system employing a PC slab just below the ITO electrode (Y.-C.Kim, S.-H. Cho, Y. W. Song, Y.-J. Lee, Y.-H. Lee, Y. R. Do, Appl. Phys.Lett. 2006, 89, 173502). The approach initially incorporated a highindex SiN_(x)/SiO₂ PC layer in an attempt to reduce TIR at theITO/substrate interface. However, the improvement in extractionefficiency was smaller than expected (˜50%) due to corrugated cathodesand losses to surface plasmons between the non-planar cathode and theunderlying organic layers. Therefore, further improvements were made byimproving the planarity of the device structure. Unfortunately, in orderto ensure a flat substrate surface, a lower refractive indexspin-on-glass (SOG) was implemented to bridge the gap between the PCpatterned substrate and the ITO electrode. The low refractive index ofthe layer increased reflections at this interface, necessitating both avery thin SOG layer as well as a high-index overcoating of SiN_(x) toachieve the maximum improvement in extraction efficiency of 85%.

In certain embodiments of the present invention, a component (e.g.,QD-LES) includes a high index of refraction (e.g., preferably >1.6, mostpreferably >1.8) material in combination with scattering agents. Suchembodiments can achieve improved light extraction efficiency. Inaddition to the out-coupling efficiency, in certain embodiments, acomponent can be tuned to function as an extremely precise colorconverter. Source light will be concentrated via waveguide-mode in thecomponent, where it will probabilistically interact with a QD/scattererformulation, converting a percentage of the photons into precisely tunedwavelengths while scattering waveguided light out of the device tocontribute to EQE and power efficiency. The resultant light can be tunedto extremely high CRIs (e.g., >85, >90, >95) while, due to the lightconversion properties and the excellent stability of color conversionmaterial CCM including in the film, maintaining CRI intensityindependence over a wide range of light intensities and OLED lifetimes.In certain embodiments, a component can be tuned to convert anylight-source containing blue light into a high CRI device, resulting ina highly versatile, highly process compatible, low-cost, andhigh-stability light-extracting substrate.

In certain embodiments, a film (including, but not limited to, a QD-LEF)comprises multi-layer stack of multi-wavelength films. In certainembodiments, a film comprises multiplexed multi-wavelength QD-LEFs orspatially dithered QD-LEFs. The multi-layer stack embodiment includesmultiple (e.g., 2 or more) QD films, ordered from the lowest energy QDfilm directly underneath the conductor material (e.g., ITO) to thehighest energy QD film at the substrate/QD-LEF interface. This structureallows light that is down converted closer to the Ph-OLED or otherlighting device to travel unimpeded through subsequent layers,eventually to be out-coupled. In higher energy outer films, the photonsemitted that travel back towards the light source, e.g., Ph-OLED, can berecycled by lower energy QDs. In all, though the down conversionefficiency will suffer from minor reabsorption losses, this loss will bemost dependent on the quantum yield (QY) of the films, which, at 80% QY,will be limited.

In certain embodiments, a QD-light emitting film comprises spatiallydithered or multiplexed multi-wavelength QD-LEFs. In this embodiment,using spatially dithered multi-color QD inks, can also greatly alleviatereabsorption issues. This design separates each QD ink into discretepatterns on the substrate, maintaining a very high absorption path forwaveguided blue excitation light while providing a very small absorptionpath for internally directed down-converted photons. Though waveguidedlight from the QDs will see this large absorption path as well, thedesign of the QD-LEF greatly limits the percentage of QD down-convertedphotons that can enter a waveguide mode. Both film designs are expectedto yield higher down-conversion efficiencies than mixed QD films andencapsulants.

Dithering or spatial dithering is a term used, for example, in digitalimaging to describe the use of small areas of a predetermined palette ofcolors to give the illusion of color depth. For example, white is oftencreated from a mixture of small red, green and blue areas. In certainembodiments, using dithering of compositions including different typesof quantum dots (wherein each type is capable of emitting light of adifferent color) disposed on and/or embedded in a surface of a substratecan create the illusion of a different color. In certain embodiments, afilm, device and/or component in accordance with embodiments of theinvention that appears to emit white light can be created from adithered pattern of features including, for example, red, green andblue-emitting quantum dots. Dithered color patterns are well known. Incertain embodiments, the blue light component of the white light cancomprise outcoupled unaltered blue excitation light and/or excitationlight that has been down-converted by quantum dots, wherein the quantumdots comprise a composition and size preselected to down-convert theexcitation light to blue.

In certain embodiments, white light can be obtained by layering filmsincluding different types of quantum dots (based on composition andsize) wherein each type is selected to obtain light having apredetermined color.

In certain embodiments, white light can be obtained by includingdifferent types of quantum dots (based on composition and size) inseparate features or pixels, wherein each type is selected to obtainlight having a predetermined color.

In certain embodiments, the quantum dots included in each layer or ineach feature or pixel can be included in a composition which furtherincludes a host material. Other additives (e.g., but not limited to,scatterers) can also be included.

As discussed above, in certain embodiments, quantum dots and/orcomposite or host materials including quantum dots will be included in aQD-LES or light-emitting device that are capable of emitting 3 or moredistinctly different predetermined peak emission wavelengths that, incombination, can simulate a white light spectrum. In certainembodiments, the light output has a high CRI, assuming afull-width-at-half-maximum (FWHM) of 35 nm for the QD emission spectrain combination with a blue-emitting light source, e.g., asky-blue-emitting Ph-OLED. In certain embodiments, core QD materialswill comprise Cd-based QD material systems, e.g., CdSe, CdZnSe, andCdZnS. Preferably, core QD materials will be prepared by a colloidalsynthesis method. These core semiconductor materials allow for maximizedsize distribution, surface quality, and color tuning in the visiblespectrum. CdZnS can be fine tuned across the entire blue region of thevisible spectrum, typically from wavelengths of 400-500 nm. CdZnSe corescan provide narrow band emission wavelengths from 500-550 nm and CdSe isused to make the most efficient and narrow band emission in the yellowto deep red part of the visible spectrum (550-650 nm). Eachsemiconductor material is chosen specifically to address the wavelengthregion of interest to optimize the physical size of the QD material,which is important in order to achieve good size distributions, highstability and efficiency, and ease of processibility. In certainembodiments, quantum dots can include a ternary semiconductor alloy. Useof a ternary semiconductor alloy can also permit use of the ratio ofcadmium to zinc in addition to the physical size of the core QD to tunethe color of emission.

In certain embodiments, a semiconductor shell material for the Cd-basedQD cores material comprises ZnS due to its large band gap leading tomaximum exciton confinement in the core. The lattice mismatch betweenCdSe and ZnS is about 12%. The presence of Zn doped into the CdSedecreases this mismatch to some degree, while the lattice mismatchbetween CdZnS and ZnS is minimal In order to grow highly uniform andthick shells onto a CdSe cores for maximum particle stability andefficiency a small amount of Cd can be doped into the ZnS growth tocreate a CdZnS shell that is somewhat graded. In certain embodiments, Cdis doped into the Zn and S precursors during initial shell growth indecreasing amounts to provide a truly graded shell, rich in Cd at thebeginning fading to 100% ZnS at the end of the growth phase. Thisgrading from CdSe core to CdS to CdZnS to ZnS can alleviate even morestrain potentially allowing for even greater stability and efficiencyfor solid state lighting applications.

In certain embodiments, QDs comprise cadmium-free materials. Examplesinclude, without limitation, QDs comprising InP or In_(x)Ga_(x-1)P. Incertain embodiments utilizing these materials, three to four distinctlydifferent peak emission wavelengths can be used to simulate a whitelight spectrum optimized for high CRI. In certain embodiments, the QDemission spectra in combination with the sky-blue Ph-OLED spectrumexhibit a full-width-at-half-maximum (FWHM) in the range of 45-50 nm orless. In certain embodiments, a predetermined CRI is achieved with 3-4specifically tuned QD emission spectra. In certain embodiments,core/shell QD comprise a core comprising InP or In_(x)Ga_(x-1)P. Incertain embodiments, an InP/ZnSeS core-shell system can be tuned fromdeep red to yellow (630-570 nm), preferably with efficiencies as high as70%. For creation of high CRI white QD-LED emitters, InP/ZnSeS QDs areused to emit in the red to yellow/green portion of the visible spectrumand In_(x)Ga_(x-1)P is used to provide yellow/green to deepgreen/aqua-green emission.

In certain embodiments, QD cores comprising InP or In_(x)Ga_(x-1)P willhave a shell on at least a portion of the core surface, the shellcomprising ZnS. Other semiconductors with a band gap similar to that ofZnS can be used. ZnS has a band gap that can lead to maximum excitonconfinement in the core. As discussed above, in certain embodimentsutilizing ZnS, InP, and/or In_(x)Ga_(x-1)P, a sphalerite (Zinc Blende)phase is adopted by all four semiconductors. The lattice mismatchbetween GaP and ZnS is less than 1%, while the lattice mismatch betweenInP and ZnS is about 8%, so doping of Ga into the InP will reduce thismismatch. Further, the addition of a small amount of Se to the initialshell growth may also improve shell growth, as the mismatch between InPand ZnSe is only 3%.

In certain embodiments, a QD Film structure includes quantum dotsincluded in a host material having a high (e.g., preferably >1.6, mostpreferably >1.8) refractive index.

In certain embodiments, a high refractive index host comprises anorganic polymer host. Monomers such as vinyl carbazole andpentabromophenyl methacrylate can be used to make high refractive indexpolymers (n=1.68-1.71) for waveguides. These monomers can be polymerizedby radical polymerization methods using UV initiators.

In certain embodiments, a high refractive index host comprises aninorganic host. In certain embodiments, sol-gel techniques can be usedto create high index inorganic hosts for the dots (TiO2, SiO2). Briefexposure to heat can gel the sol and the dots together, and minimize anydegradation of the quantum dots.

In certain embodiments, extraction of light from a layer or filmcomprising quantum dots that is included in a QD-LES can be enhanced byfurther including light scattering particles in the layer or film. Incertain embodiments of an OLED including a QD-LES, inorganic scatteringcenters such as 200 nm TiO₂ can be included in the film to increase thepathlength of the OLED (e.g., Ph-OLED) excitation light, and to helpextract quantum dot emission from the film. In certain embodimentsincluding an inorganic film, low index scattering sites such as polymerparticles or air can perform the same function.

Quantum dots that emit at different wavelengths across the visiblespectrum are preferably employed together in order to achieve a highCRI. Quantum dots differing in emission wavelength can either be mixedtogether in one layer, or individually layered on top of one another.Whereas the single layer blend is simpler from a process perspective,white emission will require careful consideration of reabsorption ofhigh energy photons by the lower energy dots. A multi-layer approach canminimize reabsorption effects, but will complicate processing. Incertain embodiments, a QD film can be deposited by a solution process.In certain embodiments, the thickness of the films (preferably >2.5 um)can be deposited by know high-performance screen printing techniques,whether laying down multiple layers or a blended layer. A screenprinting approach is a technique that can be amenable to scale-up in amanufacturing setting.

In certain embodiments, solid-state lighting device includes a lightsource and a highly efficient energy-coupling architecture including asubstrate including a layer comprising quantum dots. In certainembodiments, the light source comprises an OLED.

OLED technology has been widely viewed as having great potential forSSL. Until recently, these devices utilized fluorescent emitter specieswhich, due to their intrinsic, unmodified limitations, couldtheoretically emit at 5% external efficiency. This is due to the factthat fluorescent small molecule materials can create photons out of only25% of the electricity they consume, and that in an unmodified deviceonly ˜20% of the generated photons escapes wave-guiding. The developmentof Phosphorescent OLEDs (Ph-OLEDs), first introduced by Prof. MarcBaldo, which can theoretically harvest 100% of consumed energy, hasincreased this efficiency potential substantially with recent devicesexhibiting 40 lm/W with an EQE of 20% (unmodified by furtherout-coupling enhancements) (N. Ide et al., “Organic Light Emitting Diode(OLED) and its application to lighting devices,” SPIE Proceedings, 6333,63330M (2005)). Similarly, advances in optical out-coupling haveimproved extraction efficiencies by up to 85% (Y.-C. Kim, S.-H. Cho, Y.W. Song, Y.-J. Lee, Y.-H. Lee, Y. R. Do, Appl. Phys. Lett. 2006, 89,173502).

In certain embodiments, waveguide-mode dynamics are included with a filmor layer comprising quantum dots to provide a low-complexity, low cost,and more effective means of out-coupling blue light (e.g., blue lightemitted from a Ph-OLED light) while using QD technology to tune thisemission into high CRI light. This can be accomplished by using a highindex of refraction (n) QD film between the ITO and the substrate,effectively coupling the light specifically and predominantly into thefilm via its favorable location and n, as shown in FIG. 3.

FIG. 3(a) schematically depicts an example of an embodiment of anexample of an embodiment of a lighting device including a QD-LES showingapproximate indices of refraction and thicknesses. FIG. 3(b)schematically depicts an example of an embodiment of a typical waveguidemode intensity profile for a multi-n material stack (where the maximum nis located in the film including quantum dots) (In certain embodiments,the uppermost layer shown in FIGS. 3 (a) and 3 (b) can be a metalliclayer approximately 100 nm in thickness.) In certain embodimentsadditional layers can be included. For example, layers comprisingreflective material can be included between any layer including quantumdots and another layer (which could be another layer including quantumdots). In certain embodiments, a reflective layer comprises a higherindex material that scatters or reflects light. An example of apreferred reflective material includes silver particles. Otherreflective materials can alternatively be used.

In certain embodiments, an air gap or space can be included in a stackof layers including quantum dots in a layered arrangement of colorconversion materials CCMs to facilitate blue emissions in embodimentsincluding a blue emitting light source. In certain embodiments includingan arrangement of pixels or features, the pixels or features can beoptically isolated. Optical isolation can be achieve by separatingfeatures or pixels by air gap and/or by material having a differentrefractive index (higher or lower, but not the same). This QD filmcoupled light is then partially down-converted by the QDs in aprobabilistic manner before being scattered out of the film and out ofthe device.

FIG. 3 (c) schematically depicts an example of an embodiment of alighting device including a QD-LES, showing approximate indices ofrefraction and thicknesses and includes a substrate including amicrolens array MLA. FIG. 3 (d) schematically depicts an example of anembodiment of an example of an embodiment of a lighting device includinga component showing a typical waveguide mode intensity profile for amulti-n material stack (where the maximum n is located in the filmincluding quantum dots) (the depicted QD-LES also includes a substrateincluding a microlens array). In certain embodiments, the uppermostlayer shown in FIGS. 3(c) and 3(d) can be a metallic layer approximately100 nm in thickness.

In the embodiments depicted in FIGS. 3 (c) and (d), the film includingquantum dots coupled light is partially down-converted by the QDs beforebeing scattered out of the film and out of the device by way of anintegrated microlens array MLA. Plasmon losses at the cathode areeffectively eliminated, as a trivial waveguide mode remains at theinterface, while light that would otherwise be wave-guided is scatteredinto non-critical angles, increasing out-coupling.

In addition to increased light out-coupling, e.g., Ph-OLEDs employingQD-LESs will exhibit tunable high CRI light which is stable over thelifetime of the Ph-OLED. This is the result of immeasurably stable QDs(10,000 hours and counting) combined in a geometry such that theresultant light is uniquely independent of intensity and thus lifetimeissues. As light is coupled into the QD-LES, photons will have aprobability of being absorbed and re-emitted which, by definition, makesthe light output independent of photon flux.

Table 1 below summarizes examples of certain cadmium-containing QDcore/shell materials and material performance specifications therefor toachieve high CRI. Colloidal syntheses techniques are preferably used toengineer core-shell QD materials to emit at these predeterminedwavelengths. First, core QDs (consisting of CdSe, CdZnSe, and CdZnS)will be synthesized at the desired wavelengths of emission with narrowsize distributions and high surface quality. Next, engineered alloyshell materials (CdZnS) will be grown onto the core QDs in order toprovide the core surface passivation for high QYs and stability.

In certain embodiments, colloidal syntheses techniques will be used toattach surface ligands to quantum dots. The ligands are preferablyselected to be chemically compatible with the inorganic sol-gel andorganic host materials to be included in the films including colorconversion materials CCMs including quantum dots. This approach willprovide the most stable and efficient QD films possible.

TABLE 1 Exemplary QD performance targets for QDLS spectrum shown in FIG.2. Examples of Examples of More Preferred Predetermined Peak PreferredPreferred Preferred Core/Shell Color Wavelength (nm) FWHM (nm) QY QYCompositions Green 540 Not greater At least At least CdZnSe/CdZnS than35 65% 80% Orange 585 Not greater At least At least CdSe/CdZnS than 3565% 80% Red 630 Not greater At least At least CdSe/CdZnS than 35 75% 80%

Table 2 below summarizes examples of certain cadmium-free QD core/shellmaterials and material performance specifications therefor to achievehigh CRI. Colloidal syntheses techniques are preferably used to engineercore-shell QD materials to emit at these predetermined wavelengths.First, core QDs (consisting of In_(x)Ga_(x-1)P) will be synthesized atthe desired wavelengths of emission with narrow size distributions andhigh surface quality. Next, a shell material (e.g., a ZnSeS alloymaterial) will be grown onto the core QDs in order to provide coresurface passivation for high QYs and stability.

TABLE 2 Exemplary QD performance targets for QDLS spectrum shown in FIG.2. Examples of Examples of Preferred More Preferred Predetermined PeakFWHM Preferred Preferred Core/Shell Color Wavelength (nm) (nm) QY QYCompositions Green 520-550 Not greater At least At least InP/ZnSeS than50 60-70% 70-85% Yellow/ 560-590 Not greater At least At least InP/ZnSeSOrange than 50 60-70% 70-85% Red 610-630 Not greater At least At leastIn_(x)Ga_(x−1) than 50 60-70% 70-85% P/ZnSeS

Examples of components that may be included in a host/QD system includewithout limitation, quantum dots, monomers, prepolymers, initiators,scattering particles, and other additives. In certain embodiments to bescreen-printed, additional additives that may be necessary or desirablefor screen printing will be included. Preferably, a layer or film isdeposited using a gelling protocol that minimizes heat exposure toquantum dots, as well as a deposition approach capable of multiplelayers and patterned QD-LESs.

Preferably the composition for depositing the host/QD system will takeinto account the surface morphology and be chemically compatible withother materials included with the substrate (e.g., ITO) and Ph-OLEDdeposition processes.

It is important to note that while, for example, Ph-OLED efficiency isan important selection criterion, device stability and fabricationrepeatability are also important considerations to enhance outcouplingand down-conversion using QDs. In addition to light sources comprisingPh-OLEDs, OLEDs, and/or PLEDs any large area planar blue light sourcecan be used with a QD-LES in accordance with the invention.

A computer model can be built to simulate real-world solid-statewaveguide modes with scattering in complex material composites with aneye towards high CRI, high efficiency SSL.

Devices can be engineered to achieve predetermined emission color and/orlight characteristics by varying layer thicknesses, the composition ofcolor conversion material and the density of scattering media. Angulardependence of emission can also be taken into account using astepper-motor controlled setup.

In certain embodiments, a component, film, and/or device describedherein can include a conductive material that is suitable for use as ananode of a lighting device. An anode typically comprises a high workfunction (e.g., greater than 4.0 eV) hole-injecting conductor, such asan indium tin oxide (ITO) layer. Examples of light-transmissive ortransparent conductive materials suitable for use as an electrodeinclude ITO, conducting polymers, and other metal oxides, low or highwork function metals, conducting epoxy resins, or carbonnanotubes/polymer blends or hybrids that are at least partially lighttransmissive. An example of a conducting polymer that can be used as anelectrode material is poly(ethlyendioxythiophene), sold by Bayer AGunder the trade mark PEDOT. Other molecularly altered poly(thiophenes)are also conducting and could be used, as well as emaraldine salt formof polyaniline.

In certain embodiments, a component, film, and/or device describedherein can include a conductive material that is suitable for use as acathode, for example, a cathode comprising a low work function (e.g.,less than 4.0 eV), electron-injecting, metal, such as Al, Ba, Yb, Ca, alithium-aluminum alloy (Li:Al), a magnesium-silver alloy (Mg:Ag), orlithium fluoride-aluminum (LiF:Al). The second electrode ELT2, such asMg:Ag, can optionally be covered with a relatively thin layer ofsubstantially transparent ITO for protecting the cathode layer fromatmospheric oxidation.

In certain embodiments, a component, film, and/or device describedherein includes a substrate that is light transmissive. Preferably, thesubstrate is at least 80% transparent in the predetermined range ofwavelengths of light (visible and/or invisible); more preferably, atleast 90% transparent in the predetermined range, and most preferably atleast 95% transparent in the predetermined range. In certainembodiments, the predetermined range can be a single wavelength. Thesubstrate SUB can comprise plastic, metal, glass, or semiconductor(e.g., silicon). The substrate can be rigid or flexible.

In certain embodiments, the substrate SUB can comprise a rigid material,e.g., glass, polycarbonate, acrylic, quartz, sapphire, or other rigidmaterials with adequate transparency.

In certain embodiments, the substrate SUB can comprise a flexiblematerial, e.g., a polymeric material such as plastic or silicone (e.g.but not limited to thin acrylic, epoxy, polycarbonate, PEN, PET, PE), orother flexible material with adequate transparency.

Quantum dots (QDs), preferably semiconductor nanocrystals, permit thecombination of the soluble nature and processability of polymers withthe high efficiency and stability of inorganic semiconductors. QDs aremore stable in the presence of water vapor and oxygen than their organicsemiconductor counterparts. Because of their quantum-confined emissiveproperties, their luminescence is extremely narrow-band and yieldshighly saturated color emission, characterized by a single Gaussianspectrum. Finally, because the nanocrystal diameter controls the QDoptical band gap, fine tuning of absorption and emission wavelength canbe achieved through synthesis and structure changes, facilitating theprocess for identifying and optimizing luminescent properties. Colloidalsuspensions of QDs (also referred to as solutions) can be prepared that:(a) emit anywhere across the visible and infrared spectrum; (b) areorders of magnitude more stable than organic lumophores in aqueousenvironments; (c) have narrow full-width half-maximum (FWHM) emissionspectrum (e.g., below 50 nm, below 40 nm, below 30 nm, below 20 nm); and(d) have quantum yields up to greater than 85%.

A quantum dot is a nanometer sized particle, e.g., in the size range ofup to about 1000 nm. In certain embodiments, a quantum dot can have asize in the range of up to about 100 nm. In certain embodiments, aquantum dot can have a size in the range up to about 20 nm (such asabout 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,or 20 nm). In certain preferred embodiments, a quantum dot can have asize less than 100 Å. In certain preferred embodiments, a nanocrystalhas a size in a range from about 1 to about 6 nanometers and moreparticularly from about 1 to about 5 nanometers. The size of a quantumdot can be determined, for example, by direct transmission electronmicroscope measurement. Other known techniques can also be used todetermine nanocrystal size.

Quantum dots can have various shapes. Examples of the shape of a quantumdot include, but are not limited to, sphere, rod, disk, tetrapod, othershapes, and/or mixtures thereof.

In certain preferred embodiments, QDs comprise inorganic semiconductormaterial which permits the combination of the soluble nature andprocessability of polymers with the high efficiency and stability ofinorganic semiconductors. Inorganic semiconductor QDs are typically morestable in the presence of water vapor and oxygen than their organicsemiconductor counterparts. As discussed above, because of theirquantum-confined emissive properties, their luminescence can beextremely narrow-band and can yield highly saturated color emission,characterized by a single Gaussian spectrum. Because the nanocrystaldiameter controls the QD optical band gap, the fine tuning of absorptionand emission wavelength can be achieved through synthesis and structurechange.

In certain embodiments, inorganic semiconductor nanocrystal quantum dotscomprise Group IV elements, Group II-VI compounds, Group II-V compounds,Group III-VI compounds, Group III-V compounds, Group IV-VI compounds,Group compounds, Group II-IV-VI compounds, or Group II-IV-V compounds,alloys thereof and/or mixtures thereof, including ternary and quaternaryalloys and/or mixtures. Examples include, but are not limited to, ZnO,ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, HgO, HgS, HgSe, HgTe, AlN, AlP,AlAs, AlSb, GaN, GaP, GaAs, GaSb, GaSe, InN, InP, InAs, InSb, TlN, TlP,TlAs, TlSb, PbO, PbS, PbSe, PbTe, alloys thereof, and/or mixturesthereof, including ternary and quaternary alloys and/or mixtures.

As discussed herein, in certain embodiments a quantum dot can include ashell over at least a portion of a surface of the quantum dot. Thisstructure is referred to as a core-shell structure. Preferably the shellcomprises an inorganic material, more preferably an inorganicsemiconductor material, An inorganic shell can passivate surfaceelectronic states to a far greater extent than organic capping groups.Examples of inorganic semiconductor materials for use in a shellinclude, but are not limited to, Group IV elements, Group II-VIcompounds, Group II-V compounds, Group III-VI compounds, Group III-Vcompounds, Group IV-VI compounds, Group compounds, Group II-IV-VIcompounds, or Group II-IV-V compounds, alloys thereof and/or mixturesthereof, including ternary and quaternary alloys and/or mixtures.Examples include, but are not limited to, ZnO, ZnS, ZnSe, ZnTe, CdO,CdS, CdSe, CdTe, HgO, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP,GaAs, GaSb, GaSe, InN, InP, InAs, InSb, TlN, TlP, TlAs, TlSb, PbO, PbS,PbSe, PbTe, alloys thereof, and/or mixtures thereof, including ternaryand quaternary alloys and/or mixtures.

Examples of the most developed and characterized QD materials to dateinclude II-VI semiconductors, including CdSe, CdS, and CdTe. CdSe, witha bulk band gap of 1.73 eV (716 nm) (C. B. Murray, D. J. Norris, M. G.Bawendi, J. Am. Chem. Soc. 1993, 115, 8706), can be made to emit acrossthe entire visible spectrum with narrow size distributions and highemission quantum efficiencies. For example, roughly 2 nm diameter CdSeQDs emit in the blue while 8 nm diameter particles emit in the red.Changing the QD composition by substituting other semiconductormaterials with a different band gap into the synthesis alters the regionof the electromagnetic spectrum in which the QD emission can be tuned.For example, the smaller band gap semiconductor CdTe (1.5 eV, 827 nm)(C. B. Murray, D. J. Norris, M. G. Bawendi, J. Am. Chem. Soc. 1993, 115,8706) can access deeper red colors than CdSe. An example of another QDmaterial system includes lead containing semiconductors (e.g., PbSe andPbS). For example, PbS with a band gap of 0.41 eV (3027 nm) can be tunedto emit from 800 to 1800 nm (M. A. Hines, G. D. Scholes, Adv. Mater.2003, 15, 1844.). It is theoretically possible to design an efficientand stable inorganic QD emitter that can be synthesized to emit at anydesired wavelength from the UV to the NIR.

In certain embodiments, the QD materials are cadmium-free. Examples ofcadmium-free QD materials include InP and In an example of one approachfor preparing In_(x)Ga_(x-1)P, InP can be doped with a small amount ofGa to shift the band gap to higher energies in order to accesswavelengths slightly bluer than yellow/green. In an example of anotherapproach for preparing this ternary material, GaP can be doped with Into access wavelengths redder than deep blue. InP has a direct bulk bandgap of 1.27 eV, which can be tuned beyond 2 eV with Ga doping. QDmaterials comprising InP alone can provide tunable emission fromyellow/green to deep red; the addition of a small amount of Ga to InPcan facilitate tuning the emission down into the deep green/aqua green.QD materials comprising In_(x)Ga_(x-1)P (0<x<1) can provide lightemission that is tunable over at least a large portion of, if not theentire, visible spectrum. InP/ZnSeS core-shell QDs can be tuned fromdeep red to yellow with efficiencies as high as 70%. For creation ofhigh CRI white QD-LED emitters, InP/ZnSeS can be utilized to address thered to yellow/green portion of the visible spectrum and In_(x)Ga_(x-1)Pwill provide deep green to aqua-green emission.

Semiconductor QDs grown, for example, in the presence of high-boilingorganic molecules, referred to as colloidal QDs, yield high qualitynanoparticles that are well-suited for light-emission applications. Forexample, the synthesis includes the rapid injection of molecularprecursors into a hot solvent (300-360° C.), which results in a burst ofhomogeneous nucleation. The depletion of the reagents through nucleationand the sudden temperature drop due to the introduction of the roomtemperature solution of reagents minimizes further nucleation. Thistechnique was first demonstrated by Murray and co-workers (C. B. Murray,D. J. Norris, M. G. Bawendi, J. Am. Chem. Soc. 1993, 115, 8706) for thesynthesis of II-VI semiconductor QDs by high-temperature pyrolysis oforganometallic precursors (dimethylcadmium) in coordinating solvents(tri-n-octylphosphine (TOP) and tri-n-octylphosphine oxide (TOPO)). Thiswork was based on the seminal colloidal work by LaMer and Dinegar (V. K.LaMer, R. H. Dinegar, J. Am. Chem. Soc. 1950, 72, 4847), who introducedthe idea that lyophobic colloids grow in solution via a temporallydiscrete nucleation event followed by controlled growth on the existingnuclei.

The ability to control and separate the nucleation and growthenvironments is in large part provided by selecting the appropriatehigh-boiling organic molecules used in the reaction mixture during theQD synthesis. Example of high-boiling solvents typically include organicmolecules made up of a functional head including, for example, anitrogen, phosphorous, or oxygen atom, and a long hydrocarbon chain. Thefunctional head of the molecules attach to the QD surface as a monolayeror multilayer through covalent, dative, or ionic bonds and are referredto as capping groups. The capping molecules present a steric barrier tothe addition of material to the surface of a growing crystallite,significantly slowing the growth kinetics. It is desirable to haveenough capping molecules present to prevent uncontrolled nucleation andgrowth, but not so much that growth is completely suppressed.

This colloidal synthetic procedure for the preparation of semiconductorQDs provides a great deal of control and as a result the synthesis canbe optimized to give the desired peak wavelength of emission as well asa narrow size distribution. This degree of control is based on theability to change the temperature of injection, the growth time, as wellas the composition of the growth solution. By changing one or more ofthese parameters the size of the QDs can be engineered across a largespectral range while maintaining good size distributions.

Semiconductor QDs such as CdSe are covalently bonded solids with fourbonds per atom, which have been shown to retain the bulk crystalstructure and lattice parameters (M. G. Bawendi, A. R. Kortan, M. L.Steigerwald, L. E. Brus, J. Chem. Phys. 1989, 91, 7282). At the surfaceof a crystal, the outermost atoms do not have neighbors which they canbond to, generating surface states of different energy levels that liewithin the band gap of the semiconductor. Surface rearrangements takeplace during crystal formation to minimize the energy of these surfaceatoms, but because such a large percentage of the atoms that make up aQD are on the surface (>75% to <0.5% for QDs <1 nm to >20 nm indiameter, respectively) (C. B. Murray, C. R. Kagan, M. G. Bawendi, Annu.Rev. Mater. Sci. 2000, 30, 545), the effect on the emission propertiesof semiconductor QDs is quite large. The surface states lead tonon-radiative relaxation pathways, and thus a reduction in the emissionefficiency or quantum yield (QY).

InP and In_(x)Ga_(x-1)P are III-V semiconductors and are more covalentlybonded crystals than II-VI semiconductors. Separation of the nucleationand growth events from one another and control of the size distributionto the same extent as in II-VI semiconductor QD synthesis is thus achallenge. Because the III-V molecular precursors in general associatemore strongly with the elements oxygen, nitrogen, sulfur andphosphorous, compared with the II-VI molecular precursors, a morereactive molecular precursor is required in order to get semiconductorformation at 200-300° C. in solution. The higher reactivity of theprecursors causes the nucleation and growth stages to overlap, leadingto broader size distributions, lower quality QDs, and lower quantumefficiencies. By tuning the molecular precursor reactivities andexploring how different concentrations of different capping moleculeseffect nucleation and growth during the reaction in the InP andIn_(x)Ga_(x-1)P semiconductor systems, we will manipulate and controlnucleation and growth to yield tight size distributions, high stability,and high quantum efficiencies.

When molecules are chemically bound or otherwise attached to the surfaceof a QD, they help to satisfy the bonding requirements of the surfaceatoms, eliminating many of the surface states and correspondingnon-radiative relaxation pathways. This can provide QDs with goodsurface passivation and higher QY as well as higher stability than QDswith poor surface passivation. Thus, design and control of the growthsolution and processing can provide good passivation of the surfacestates and results in high QYs. Furthermore, these capping groups canplay a role in the synthetic process as well by mediating particlegrowth and sterically stabilizing the QDs in solution.

An effective method for creating QDs with high emission efficiency andstability is to grow an inorganic semiconductor shell onto QD cores.Core-shell type composites rather than organically passivated QDs aredesirable for incorporation into solid-state structures, such as a solidstate QD-LED device, due to their enhanced photoluminescence (PL) andelectroluminescence (EL) quantum efficiencies and a greater tolerance tothe processing conditions necessary for device fabrication (B. O.Dabbousi, J. Rodriguez-Viejo, F. V. Mikulec, J. R. Heine, H. Mattoussi,R. Ober, K. F. Jensen, M. G. Bawendi, J. Phys. Chem. B 1997, 101, 9463;B. O. Dabbousi, O. Onitsuka, M. G. Bawendi, M. F. Rubner, Appl. Phys.Lett. 1995, 66, 1316; M. A. Hines, P. Guyot-Sionnest, J. Phys. Chem.1996, 100, 468; S. Coe-Sullivan, W. K. Woo, J. S. Steckel, M. G.Bawendi, V. Bulović, Org. Electron. 2003, 4, 123. When a shell of alarger band gap material is grown onto a core QD, for example ZnS (bandgap of 3.7 eV) onto CdSe, the majority of the surface electronic statesare passivated and a 2 to 4 fold increase in QY is observed (B. O.Dabbousi, J. Rodriguez-Viejo, F. V. Mikulec, J. R. Heine, H. Mattoussi,R. Ober, K. F. Jensen, M. G. Bawendi, J. Phys. Chem. B 1997, 101, 9463).The presence of a shell of a different semiconductor (in particular onethat is more resistant to oxidation) on the core also protects the corefrom degradation.

Due to the superior properties of core-shell materials outlined above, aquantum dot including a core-shell structure is preferred. A factor inQD core-shell development is the crystal structure of the core and shellmaterial as well as the lattice parameter mismatch between the two. Thelattice mismatch between CdSe and ZnS is 12% (B. O. Dabbousi, J.Rodriguez-Viejo, F. V. Mikulec, J. R. Heine, H. Mattoussi, R. Ober, K.F. Jensen, M. G. Bawendi, J. Phys. Chem. B 1997, 101, 9463), which isconsiderable, but because only a few atomic layers (e.g., from 1 to 6monolayers) of ZnS are grown onto CdSe the lattice strain is tolerated.The lattice strain between the core and shell materials scales with thethickness of the shell. As a result, a shell that is too thick can causedislocations at the material interface and will eventually break off ofthe core. Doping a shell (e.g., ZnS shell with Cd) can relieve some ofthis strain, and as a result thicker shells (in this example, CdZnS) canbe grown. The effect is similar to transitioning more gradually fromCdSe to CdS to ZnS (the lattice mismatch between CdSe and CdS is about4% and that between CdS and ZnS about 8%), which provides for moreuniform and thicker shells and therefore better QD core surfacepassivation and higher quantum efficiencies.

In certain embodiments including a QD core comprising InP orIn_(x)Ga_(x-1)P, a preferred semiconductor shell material comprises ZnS.ZnS is preferred due to its large band gap leading to maximum excitonconfinement in the core. Preferably, when the QDs comprising ZnS, InP,and/or In_(x)Ga_(x-1)P, each is a sphalerite (Zinc Blende) phasematerial. The lattice mismatch between GaP and ZnS is less than 1%,while the lattice mismatch between InP and ZnS is about 8%, so doping ofGa into the InP will reduce this mismatch. Further, the addition of asmall amount of Se to the initial shell growth may also improve shellgrowth, as the mismatch between InP and ZnSe is only 3%.

While core-shell particles exhibit improved properties compared tocore-only systems, good surface passivation with organic ligands isstill desirable for maintaining quantum efficiency of core-shell QDs.This is due to the fact that the particles are smaller than the excitonBohr radius, and as a result the confined excited-state wavefunction hassome probability of residing on the surface of the particle even in acore-shell type composite. Strong binding ligands that passivate thesurface improve the stability and efficiency of core-shell QD material.

One example of a method for synthesizing quantum dots includes colloidalsynthesis techniques as described above, typically exhibit highlysaturated color emission with narrow full-width-at-half-maximums (FWHM),preferably less than 30 nm. The number of accessible emission colors isvirtually unlimited, due to the fact that the QD peak emission can betailored by selecting the appropriate material system and size of thenanoparticles. Colloidally synthesized red, green and blue Cd-based QDscan routinely achieve solution quantum yields on the order of 70-80%,with peak emission wavelength reproducibility within +/−2% and FWHM lessthan 30 nm.

In certain embodiments, QDs include a core comprising InP. Preferablysuch QDs have a 50% solution quantum yields or higher. In certainembodiments, such QDs are prepared by a colloidal synthesis process. Anexample of a process for preparing QDs including a core comprising InPor other III-V semiconductor materials is described in U.S. PatentApplication No. 60/866,822 of Clough, et al., filed 21 Nov. 2006, thedisclosure of which is hereby incorporated herein by reference in itsentirety).

InP/ZnSeS QDs can achieve solution quantum yields up to 70%, with peakemission wavelength reproducibility within +/−2% and FWHM less than 60nm, examples of which are tabulated below in Table 3.

TABLE 3 Deep Yellow/ COLOR Deep Red Red Orange Orange Orange YellowWavelength 630 nm 619 nm 604 nm 593 nm 580 nm 569 nm peak Quantum 62%63% 70% 67% 60% 57% Yield

Quantum dots included in various aspects and embodiments of theinventions contemplated by this disclosure are preferably members of apopulation of quantum dots having a narrow size distribution. Morepreferably, the quantum dots comprise a monodisperse or substantiallymonodisperse population of quantum confined semiconductor nanoparticles.

Examples of other quantum dots materials, methods, and QD-LEDs that maybe useful with the present invention include those described in:International Application No. PCT/US2007/13152, entitled “Light-EmittingDevices And Displays With Improved Performance”, of Seth Coe-Sullivan,et al., filed 4 Jun. 2007, U.S. Provisional Patent Application No.60/866,826, filed 21 Nov. 2006, entitled “Blue Light EmittingSemiconductor Nanocrystal Materials And Compositions And DevicesIncluding Same”, of Craig Breen et al.; U.S. Provisional PatentApplication No. 60/866,828, filed 21 Nov. 2006, entitled “SemiconductorNanocrystal Materials And Compositions And Devices Including Same”, ofCraig Breen et al.; U.S. Provisional Patent Application No. 60/866,832,filed 21 Nov. 2006, entitled “Semiconductor Nanocrystal Materials AndCompositions And Devices Including Same”, of Craig Breen et al.; U.S.Provisional Patent Application No. 60/866,833, filed 21 Nov. 2006,entitled “Semiconductor Nanocrystal And Compositions And DevicesIncluding Same”, of Dorai Ramprasad; U.S. Provisional Patent ApplicationNo. 60/866,834, filed 21 Nov. 2006, entitled “Semiconductor NanocrystalAnd Compositions And Devices Including Same”, of Dorai Ramprasad; U.S.Provisional Patent Application No. 60/866,839, filed 21 Nov. 2006,entitled “Semiconductor Nanocrystal And Compositions And DevicesIncluding Same”, of Dorai Ramprasad; U.S. Provisional Patent ApplicationNo. 60/866,840, filed 21 Nov. 2006, entitled “Blue Light EmittingSemiconductor Nanocrystal And Compositions And Devices Including Same”,of Dorai Ramprasad; and U.S. Provisional Patent Application No.60/866,843, filed 21 Nov. 2006, entitled “Semiconductor Nanocrystal AndCompositions And Devices Including Same”, of Dorai Ramprasad. Thedisclosures of each of foregoing listed patent applications are herebyincorporated herein by reference in their entireties.

An example of a deposition technology that may be useful in applyingquantum dot materials and films or layers including quantum dotmaterials to a surface that may be useful with the present inventionincludes microcontact printing.

QD materials and films or layers including QD materials can be appliedto flexible or rigid substrates by microcontact printing, inkjetprinting, etc. The combined ability to print colloidal suspensions ofQDs over large areas and to tune their color over the entire visiblespectrum makes them an ideal lumophore for solid-state lightingapplications that demand tailored color in a thin, light-weight package.QDs and films or layer including QDs can be applied to a surface byvarious deposition techniques. Examples include, but are not limited to,those described in International Patent Application No.PCT/US2007/08873, entitled “Composition Including Material, Methods OfDepositing Material, Articles Including Same And Systems For DepositingMaterial”, of Seth A. Coe-Sullivan, et al., filed 9 Apr. 2007,International Patent Application No. PCT/US2007/09255, entitled “MethodsOf Depositing Material, Methods Of Making A Device, And Systems AndArticles For Use In Depositing Material”, of Maria J, Anc, et al., filed13 Apr. 2007, International Patent Application No. PCT/US2007/08705,entitled “Methods And Articles Including Nanomaterial”, of SethCoe-Sullivan, et al, filed 9 Apr. 2007, International Patent ApplicationNo. PCT/US2007/08721, entitled “Methods Of Depositing Nanomaterial &Methods Of Making A Device” of Marshall Cox, et al., filed 9 Apr. 2007,U.S. patent application Ser. No. 11/253,612, entitled “Method And SystemFor Transferring A Patterned Material” of Seth Coe-Sullivan, et al.,filed 20 Oct. 2005, U.S. patent application Ser. No. 11/253,595,entitled “Light Emitting Device Including Semiconductor Nanocrystals”,of Seth Coe-Sullivan, et al., filed 20 Oct. 2005, International PatentApplication No. PCT/US2007/14711, entitled “Methods for DepositingNanomaterial, Methods For Fabricating A Device, And Methods ForFabricating An Array Of Devices”, of Seth Coe-Sullivan, filed 25 Jun.2007, International Patent Application No. PCT/US2007/14705, “Methodsfor Depositing Nanomaterial, Methods For Fabricating A Device, AndMethods For Fabricating An Array Of Devices And Compositions”, of SethCoe-Sullivan, et al., filed 25 Jun. 2007, and International ApplicationNo. PCT/US2007/14706, entitled “Methods And Articles IncludingNanomaterial”, of Seth Coe-Sullivan, et al., filed 25 Jun. 2007. Each ofthe foregoing patent applications is hereby incorporated herein byreference in its entirety.

Additional information concerning quantum dot materials, various methodsincluding quantum dots, and devices including quantum dot materials isincluded in the following publications are hereby incorporated herein byreference in their entireties: P. Kazlas, J. Steckel, M. Cox, C. Roush,D. Ramprasad, C. Breen, M. Misic, V. DiFilippo, M. Anc, J. Ritter and S.Coe-Sullivan “Progress in Developing High Efficiency Quantum DotDisplays” SID '07 Digest, P176 (2007); G. Moeller and S. Coe-Sullivan“Quantum-Dot Light-Emitting Devices for Displays” SID '06 Digest (2006);J. S. Steckel, B. K. H. Yen, D. C. Oertel, M. G. Bawendi, “On theMechanism of Lead Chalcogenide Nanocrystal Formation”, Journal of theAmerican Chemical Society, 128, 13032 (2006); J. S. Steckel, P. Snee, S.Coe-Sullivan, J. P. Zimmer, J. E. Halpert, P. Anikeeva, L. Kim, M. G.Bawendi, and V. Bulovic, “Color Saturated Green-Emitting QD-LEDs”,Angewandte Chemie International Edition, 45, 5796 (2006); P. O.Anineeva, C. F. Madigan, S. A. Coe-Sullivan, J. S. Steckel, M. G.Bawendi, and V. Bulović, “Photoluminescence of CdSe/ZnS Core/ShellQuantum Dots Enhanced by Energy Transfer from a Phosphorescent Donor,”Chemical Physics Letters, 424, 120 (2006); Y. Chan, J. S. Steckel, P. T.Snee, J.-Michel Caruge, J. M. Hodgkiss, D. G. Nocera, and M. G. Bawendi,“Blue semiconductor nanocrystal laser”, Applied Physics Letters, 86,073102 (2005); S. Coe Sullivan, W. woo, M. G. Bawendi, V. Bulovic“Electroluminescence of Single Monolayer of Nanocrystals in MolecularOrganic Devices”, Nature (London) 420, 800 (2002); S. Coe-Sullivan, J.S. Steckel, L. Kim, M. G. Bawendi, and V. Bulovic, “Method forfabrication of saturated RGB quantum dot light-emitting devices”, Proc.of SPIE Int. Soc. Opt. Eng., 108, 5739 (2005); J. S. Steckel, J. P.Zimmer, S. Coe-Sullivan, N. Stott, V. Bulović, M. G. Bawendi, “BlueLuminescence from (CdS)ZnS Core-Shell Nanocrystals”, Angewandte ChemieInternational Edition, 43, 2154 (2004); Y. Chan, J. P. Zimmer, M. Stroh,J. S. Steckel, R. K. Jain, M. G. Bawendi, “Incorporation of LuminescentNanocrystals into Monodisperse Core-Shell Silica Microspheres”, AdvancedMaterials, 16, 2092 (2004); J. S. Steckel, N. S. Persky, C. R. Martinez,C. L. Barnes, E. A. Fry, J. Kulkarni, J. D. Burgess, R. B. Pacheco, andS. L. Stoll, “Monolayers and Multilayers of [Mn12O12(O2CMe)16]”, NanoLetters, 4, 399 (2004); Y. K. Olsson, G. Chen, R. Rapaport, D. T. Fuchs,and V. C. Sundar, J. S. Steckel, M. G. Bawendi, A. Aharoni, U. Banin,“Fabrication and optical properties of polymeric waveguides containingnanocrystalline quantum dots”, Applied Physics Letters, 18 4469 (2004);D. T. Fuchs, R. Rapaport, G. Chen, Y. K. Olsson, V. C. Sundar, L. Lucas,and S. Vilan, A. Aharoni and U. Banin, J. S. Steckel and M. G. Bawendi,“Making waveguides containing nanocrystalline quantum dots”, Proc. ofSPIE, 5592, 265 (2004); J. S. Steckel, S. Coe-Sullivan, V. Bulović, M.G. Bawendi, “1.3 μm to 1.55 μm Tunable Electroluminescence from PbSeQuantum Dots Embedded within an Organic Device”, Adv. Mater., 15, 1862(2003); S. Coe-Sullivan, W. Woo, J. S. Steckel, M. G. Bawendi, V.Bulović, “Tuning the Performance of Hybrid Organic/Inorganic Quantum DotLight-Emitting Devices”, Organic Electronics, 4, 123 (2003); and thefollowing patents of Robert F. Karlicek, Jr., U.S. Pat. No. 6,746,889“Optoelectronic Device with Improved Light Extraction”; U.S. Pat. No.6,777,719 “LED Reflector for Improved Light Extraction”; U.S. Pat. No.6,787,435 “GaN LED with Solderable Backside Metal”; U.S. Pat. No.6,799,864 “High Power LED Power Pack for Spot Module Illumination”; U.S.Pat. No. 6,851,831 “Close Packing LED Assembly with VersatileInterconnect Architecture”; U.S. Pat. No. 6,902,990 “SemiconductorDevice Separation Using a Patterned Laser Projection”; U.S. Pat. No.7,015,516 “LED Packages Having Improved Light Extraction”; U.S. Pat. No.7,023,022 “Microelectronic Package Having Improved Light Extraction”;U.S. Pat. No. 7,170,100 “Packaging Designs for LEDs”; and U.S. Pat. No.7,196,354 “Wavelength Converting Light Emitting Devices”.

Additional information relating to semiconductor nanocrystals and theiruse is also found in U.S. Patent Application No. 60/620,967, filed Oct.22, 2004, and Ser. No. 11/032,163, filed Jan. 11, 2005, U.S. patentapplication Ser. No. 11/071,244, filed 4 Mar. 2005. Each of theforegoing patent applications is hereby incorporated herein by referencein its entirety.

Additional information relating to organic electroluminescent devices(OLEDs) is found in the following publications, each of which is herebyincorporated herein by reference in its entirety: “High efficiencyphosphorescent emission from organic electroluminescent devices”, M. A.Baldo, D. F. O'Brien, Y. You, A. Shoustikov, S. Sibley, M. E. Thompsonand S. R. Forrest. Nature. 395. 151-154 (1998); “High efficiencyfluorescent organic light-emitting devices using a phosphorescentsensitizer”, M. A. Baldo, M. E. Thompson and S. R. Forrest. Nature. 403.750-753 (2000); “The prospects for electrically-pumped organic lasers”,M. A. Baldo, R. I. Holmes and S. R. Forrest. Physical Review B. 66.035321 (2002); “Very high-efficiency green organic light-emittingdevices based on electro-phosphorescence”, M. A. Baldo, S. Lamansky, P.E. Burrows, M. E. Thompson and S. R. Forrest. Applied Physics Letters.75. 4-6 (1999); “Simplified calculation of dipole energy transport in amultilayer stack using dyadic Green's functions”, K. Celebi, T. D.Heidel, and M. A. Baldo. Optics Express, 15 1762-1772 (2007);“Extrafluorescent Electroluminescence in Organic Light EmittingDevices”, M. Segal, M. Singh, K. Rivoire, S. Difley, T. Van Voorhis, andM. A. Baldo. Nature Materials. 6. 374-378 (2007); “Saturated andefficient blue phosphorescent organic light emitting devices withLambertian angular emission”, Mulder, C. L., K. Celebi, K. M. Milaninia,and M. A. Baldo. Applied Physics Letters. 90. 211109 (2007); and“Excitonic singlet triplet ratios in molecular and polymeric organicsemiconductors”, M. Segal, M. A. Baldo, R. J. Holmes, S. R. Forrest, andZ. G. Soos. Physical Review B. 68. 075211 (2003).

As used herein, “top” and “bottom” are relative positional terms, basedupon a location from a reference point. More particularly, “top” meansfarthest away from the substrate, while “bottom” means closest to thesubstrate. For example, for a light-emitting device that optionallyincludes two electrodes, the bottom electrode is the electrode closestto the substrate, and is generally the first electrode fabricated; thetop electrode is the electrode that is more remote from the substrate,on the top side of the light-emitting material. The bottom electrode hastwo surfaces, a bottom surface closest to the substrate, and a topsurface further away from the substrate. Where, e.g., a first layer isdescribed as disposed or deposited “over” a second layer, the firstlayer is disposed farther away from substrate. There may be other layersbetween the first and second layer, unless it is otherwise specified.For example, a cathode may be described as “disposed over” an anode,even though there are various organic and/or inorganic layers inbetween.

As used herein, the singular forms “a”, “an” and “the” include pluralunless the context clearly dictates otherwise. Thus, for example,reference to a nanomaterial includes reference to one or more of suchmaterials.

All the patents and publications mentioned above and throughout areincorporated in their entirety by reference herein. Further, when anamount, concentration, or other value or parameter is given as either arange, preferred range, or a list of upper preferable values and lowerpreferable values, this is to be understood as specifically disclosingall ranges formed from any pair of any upper range limit or preferredvalue and any lower range limit or preferred value, regardless ofwhether ranges are separately disclosed. Where a range of numericalvalues is recited herein, unless otherwise stated, the range is intendedto include the endpoints thereof, and all integers and fractions withinthe range. It is not intended that the scope of the invention be limitedto the specific values recited when defining a range.

Other embodiments of the present invention will be apparent to thoseskilled in the art from consideration of the present specification andpractice of the present invention disclosed herein. It is intended thatthe present specification and examples be considered as exemplary onlywith a true scope and spirit of the invention being indicated by thefollowing claims and equivalents thereof.

What is claimed is:
 1. A lighting device including: a substratecomprising a material that is transparent to light within apredetermined range of wavelengths, the substrate including one or moreoptical member on a surface of the substrate; a color conversionmaterial comprising quantum dots and disposed over a predeterminedregion of a surface of the substrate opposite the optical member; afirst electrode disposed over at least a portion of the color conversionmaterial, the first electrode being transparent to light within a secondpredetermined range of wavelengths; an emissive layer disposed over atleast a portion of the first electrode, wherein the emissive layercomprises a material capable of emitting blue light; and a secondelectrode disposed over the emissive layer.
 2. A lighting device inaccordance with claim 1, wherein the optical member comprises amicrolens array.
 3. A lighting device in accordance with claim 1,wherein the optical member comprises a micro-relief structure.
 4. Alighting device in accordance with claim 1, wherein the optical membercomprises a substantially hemispherical surface.
 5. A lighting device inaccordance with claim 1, wherein the optical member comprises a curvedsurface.
 6. A lighting device in accordance with claim 1, wherein thecolor conversion material including quantum dots is included in a layercomprising a predetermined arrangement of sub-layers disposed over apredetermined region of a surface of the substrate.
 7. A lighting devicein accordance with claim 1, wherein the color conversion materialincluding quantum dots is included in a layered arrangement includingtwo or more layers disposed over a predetermined region of a surface ofthe substrate.
 8. A lighting device in accordance with claim 1, whereinthe device further comprises one or more charge transport layers betweenthe first and second electrodes.
 9. A lighting device in accordance withclaim 1, wherein the device further comprises one or more chargeinjection layers between the first and second electrodes.
 10. A lightingdevice in accordance with claim 1, wherein the device comprises an OLED.11. A lighting device in accordance with claim 1, wherein the emissivelayer comprises quantum dots.
 12. A lighting device in accordance withclaim 1, wherein the device comprises a thin film light emitting device.13. A lighting device in accordance with claim 1, wherein the devicecomprises a thin film electroluminescent device.
 14. A light emittingdevice in accordance with claim 6, wherein a first portion of thesub-layers comprises optically transparent scatterers or non-scatteringmaterial, a second portion of the sub-layers comprises quantum dotscapable of emitting red light, and a third portion of the sub-layerscomprises quantum dots capable of emitting green light.
 15. A lightemitting device in accordance with claim 6, wherein a first portion ofthe sub-layers comprises optically transparent scatterers ornon-scattering material, and a second portion of the sub-layerscomprises quantum dots capable of emitting yellow light.
 16. A lightemitting device in accordance with claim 7, wherein the layeredarrangement comprises a first film including quantum dots capable ofemitting red light, and a second film including quantum dots capable ofemitting green light, and a third film including scatterers ornon-scattering material to outcouple light.
 17. A light emitting devicein accordance with claim 7, wherein the layered arrangement comprises afirst film including quantum dots capable of emitting yellow light, asecond film including scatterers or non-scattering material to outcouplelight.
 18. A lighting device in accordance with claim 16, wherein thefirst film, the second film, and the third film are formed in order withthe first film being nearest the first electrode.